The fast cavalry units are primarily used for raiding, kill ranged units, snipe siege to protect your own or ally’s ranged units. S.Riders are excellent for all of these.
Actually most important for Dravidians because fighting against melee is not the purpose of cavalry units and Dravidians have the worst stable.
Turks get an extra p.armor on Scouts and archer players just add more spears. Bengalis aren’t weak for longer feudal plays. Its early-mid castle age where they fall apart with no options. Free cavalry armor will be a great bonus completely wasted on a civ that gets no knights and a uu that doesn’t depend on cavalry armor class.
Boom into light cav?? 
Those are very very very weak strategies. Elephants are a strict no for 1v1. So the only option is Rathas. Obviously you can’t play rathas like how people play Conqs or Janissaries but rather like Camel archer, keeping them a part of the imp composition.
Italians, Portugese, Byzantines, Bohemians and many more either have all monk techs or miss just heresy , have great siege with siege engineers and miss just 1 upgrade on infantry or range. Full upgrades on arbs and infantry is no where close to compensating for the lack of canons, siege engineers and monk techs. That’s why Bohemians, Byzantines are top 10 and Dravidians is at least bottom 15 if not bottom 10.
And then those light cav won’t be able to chase opponent light cav, opponent light cav will snipe your slow fervor-less monks, you have to invest a lot of that extra wood into making multiple spears. Somehow you did a terrific job and won the relic war, then what. You boom into what exactly? And how do you kill enemy canons or onagers with siege engineers? What will you do against civs with redemption and illumination and have good ranged units of their own?
Because you’d still lose to the meta uu into imp + canons civs and other top tier closed map civs like Britons, Byzantines, Burgundians, Bohemians etc. So it will perhaps become a top-15. What’s wrong in a D tier open map civ being top-10 or top-15 on closed maps?
So sorry that I disappointed you and didn’t come up with some useless non-buff which doesn’t impact the gameplay of these civs like medical corps +25 hp per minute, cost of Mahayana down by 100 food or urumi swordsman +5 hp.
These civs are definitely not going to get knights. So either an already decent uu should be strengthened to make it a fully uu dependent civ or some other line of units should become a viable option.
Its not actually. First of all EA as a replacement to CA is a terrible idea. And civs which lack knights get eagles or stronger camels for mobility and to fight against standard meta combos. Bulgarians, Malay or Cumans are a L2P issue as they have unorthodox bonuses that need a deviation from the standard meta play. Bengalis just lack 2 major unit lines and have missing upgrades for other generic units as well. There’s no dark age bonus or feudal age military bonus for feudal aggression, to get a significant lead in feudal age. Late imp isn’t great either as they don’t have hussar, last infantry armor for halbs and the elephant rams cost more gold, so the extra vills from pop space is only going to be sufficient to keep up for these late game weaknesses.
while it does make Elephant archers are a bit more viable, they’re still going to be unusable. Even with both of these changes tied together, it will only compensate for the lack of Parthian tactics and Elite elephant archers will still take 13 or 14 damage from each elite skirmisher hit which would make them quite fragile and cost ineffective against skirms in imp.
Elephants aren’t 1v1 units and Hera lost the game purely because of that long swords addition. His chat trolls and he trolls himself for that game. No one plays long swords against non-eagle civs.
Agree that both together would be a bit too much of a buff. Editing the original post.
Even for pros, its difficult to switch back and forth at that stage of the game where attacks happen at multiple sites on the map.