Cheaper cataphract upgrades, which is kind of a big deal to reach that late game power later.
As of early game bonuses, the prominence of palissade and house walls let them enjoy their bonus HP on all buildings.
That would be the Chinese bonus then.
No, the Roman empire was not conquered by Obelix 11
Byzantines buff:
Cataphract gains +0/1 armor
Relics give 1.5Ă-Ă2 gold
Increases the quality of cataphracts for their price and for 1 vs 1 increases the ability to sustain their gold costs over time provided they gain relics.
The whole point of cataphracts is that while they arenât countered by usual cavalry counters they perform worse against archers, so giving them more pierce armour would go against this. Also, why give them a better version of the aztec bonus when they are among the best civs for trash wars?
With +1 pierce armor it buffs the cataphract against grazing arrow fire - it will still be properly mauled when hit by concentrated arrows so wonât change the mechanic in general.
The relic bonus specifically will allow them a way to fight properly 1 vs 1 with a better trickle of gold to supply their gold heavy unit into battle. Especially since they use so much trash, itâs not like they can afford to sell all of that precious wood and food after the market hits 14-17 per 100 just because they need the gold, especially on arabia, and unless they have a large amount of relics, itâs almost hopeless to field a proper number of cataphracts in the lategame 1vs1 arabia before having to rely near soley on trash.
I tend to not build trash to fight trash or often in general, so my opinion may differ, coming from being a Teuton main -
considering the cataphract takes literally half damage or less from the normal cavalry counters, it needs that archer weakness as a balancing mechanism.
They have cheaper skirms to protect their cataphracts against archers.
Also, the relic bonus is just the aztec bonus, but better. If i had to suggest a relic bonus, i would say âtheir TC starts with one relicâ. This relic could be one of the 5 per map on an extra one. However, i dint think they need a gold bonus. I prefer the initial explored area bonus suggested above by @FlorianOpel
That bonus would be helpful to prevent obelix laming
@WolfKhanGen, I dare to disagree with you on your point.
I see where you are going by buffing the gold income and the cataphracts, but remember that the big picture says something else: Byzantines are late game power houses, especially in team games, where they can silence every archer or knight civilization. Improving their late game, doesnât solve the problems of their slow start.
Please, look again at the statistics from aoestats.io - https://aoestats.io/civ/Byzantines/RM_1v1. It is clear that there is nothing working for them within the 20-30 minute period. Yes, we can argue that from the Feudal age they can use their cheaper spearmen and skirmishers, but this is only a defensive strategy, which is not enough to overcome the enemy. Also, their savings on food and wood are probably not that significant in comparison to other civilizations, like Japanese with their -50% wood on economy buildings.
Probably I am weak player and donât know how to use the Byzantines properly. Daut, Hera and The Viper had a few games last months, where they crushed with trash units, but I am too far from that level. I would love a simple early bonus. As @JokerPenguin593 noticed, this could transition to a crazy combo with the Vietnamese for an instance. 
Byzantine has free town watch so exploration thing is covered. It is just helpful from feudal instead of dark age. Aztec has relic bonus so Byzantine having 1.5x to 2x would be just op.
Adding PA to cataphract? Iâm going to wait those heroes writing essay length posts crying out âcataphract OP pls NERFâ followed by 350+ posts. 11
About the idea of a line of sight bonus, remember line of sight is different from a given area having been explored. This is not the chinese bonus nor is it encompased by free town watch. We are only talking about the geography of the map having been seen here.
You guys are right about them needing something that would help in early game. Infact its kind of a bit odd that they are a late game powerhouse as the later in their history you examine the less land they controlled and the weaker their army had becomeâŠ
Reduced range trebs in Castle age? Or Trebs from the seige workshop? Idk Im kind of stuck on Trebs myself as the Byzantines invented the dang things.
A relic buff has a lot of historical basis as it was Constineâs mother who went to Isreal & dug up the True Cross and I think âfoundâ some other artifacts there that ended up being transfered to European nations.
The problem with Byzantines is that
-their lategame is superb, cheap FU skirms just wreck everything and they have a very nice transition into it (early imp arb). They also have bbc and siege ram.
-they dominate water maps where you dont have much space on water eg 4 lakes.
-They start the game at a deficit as their bonuses dont really kick in until castle age - and even then are slow to take off.
We could actually see this in RBW1: Byz were a suddenly a contested pick, as their weak dark age didnt come into play and 4 lakes was in the map pool. So we see how close the civ is to beeing good! That also means you have to be careful when buffing them: Once they easily get to either FU catas or their late imp trashspam, they are really hard to beat.
That beeing said, some more early defense bonuses might be nice to let them actually get there. The idea with an pre explored area sounds nice, another funny thing would be additional stone/gold piles at their starting TC - meaning they always get a little bit of safe gold access. For early castle, you could also give them Town Patrol for free.
True, this is no game breaking.
I would reduce its cost a bit for everyone and give it for free to byzantines as a bonus.
Maybe give them free upgrade BBT or 25% discount on building BBT since theyâre defensive civ is good. Make them harder to be raided.
Wont change the game at all. Their late imp is fine, its early on they struggle.
Thanks for reminding us of RDW1. The Byzantines are a damn nice civilization and indeed, giving them an early advantage could spiral out of control. I think that the remedy could be reducing their late game by removing some of the last Blacksmith upgrades, if the outcome is a S+ tier civilization 
Somebody must read their historyâŠ
Anyway regarding buff, historicaly speaking they need some kind of horse buff.
Give them bloodlines and you have a strong castle age civ with passable feudal they lack the last blacksmith upgrade.
Afraid of their camels being op? Then reduce the cost decrease, afraid of catas then increase cost or reduce base hitpoints a bit.
This can come at the cost of losing something on the infantry side, how about the last armor upgrade?
Another idea would be to start them with 250 gold. They had tremendous economic advantage over everybody in the dark & feudal ages.
In this case no bloodlines of course!
Actualy i think this would be the most interesting solution. Increase starting gold.
Please read Aztecs bonuses.
Yes adding +150 gold when Aztecs have +50 is too interesting.
If it were simply a buff to the early game -
Pallisade cost reduced from 2 -1
Stone wall cost reduced from 5-3 or 2
Pallisade gate cost reduced from 20 -10
Stone gate cost reduced from 30-15
Or in a different fashion - walls and gates are built 50% faster
Cost reduction is Mayan team bonus. I think building faster better.
Well aztec have the best eco bonus in the game , villager resource load. + 50 gold, + 11% faster Barracks.
Instead of extra gold or cheaper walls they could start with extra stone
No civ starts with extra stone.