I very much hope the Devs are not afraid of implementing some AoE3 features.
And people should also not forget AoM. If you ignore the mythical parts you have a pre gunpowder era Age of Empires game.
Some features only made sense because of the setting like the shipments. Somethings were indirectly done because of the settings like villagers not having to to drop the resources because having a lot of infrastructure in the new world would look strange.
Thing they should copy from AoE3 (AoM):
Training units in groups of up to 5. Having them spawn together means they have a higher chance of fighting of enemies and you have to micro less because you spawn units less often.
Every Civ has multiple viable units to build and they have a clear counter. Not every civ needs every type of unit. Some units can differ from the norm.
None annoying ways to get gold (coin in AoE3) in the endgame. I think it’s to easy in AoE3 but the trading in AoE2 didn’t feel fun. The plantations (we maybe already saw them in the trailer) should just give nearly as much gold as the mills/fields give food. Maybe making them give food and gold (50/50 or even 50/25 food/gold).
Wales giving infinite gold but only 4 fishing boots at once is a nice feature. Maybe make normal fish infinite too but only one boot like in AoM.
A modified version of the homecity cards. No unit or resource shipments only technologies that you have to play normal resources for but you can customize which ones you have access to. This way the civs could have more variety. So you can choose of you either want to improve the strengths of your civilisation or equal out it’s weaknesses. This is hard to balance and might end up with everyone picking the same ones.
Let some military units construct some buildings. In AoE3 some civs have a card that let’s some units construct milliary buildings and in AoM all Norse infantry does. Having to pull workers to the front feels wrong. Let the soldiers at last build palisades. That’s something that should depend on the civ of course.
The heroes should be like the war chiefs in AoE3. Having a passive bonus for the units around them but no super strong active abilities like WC3 heroes. Let them construct some buildings too.
I don’t think the AoE3 style treasure would fit though. Also I don’t think you should start with one. The hero should be trained later at around age 3.
Also something like the Japanese Daimyo from AoE3 might be something worth considering. Being able to train troops at the front and giving them a stat boost.
Secretly the biggest feature I want from AoE3/AoM are the possibilities in the Editor. AoE2 triggers are so limited compared to AoE3. AoE3 has so many nice things that can be done that weren’t possible in AoE2 or very annoying to implement.
Trading Posts wont really fit in but I really like the native allies in AoE3 that give you limited special units (that don’t cost population) and some unique technologies. It would be nice to have something similar in AoE4.
Big ships. Ships should always cost more than any land unit (Besides Heroes maybe) and they should always be able to transport units. Make them like small swimming castles/towers because that’s what they were. Archers should shoot from ships like if they were towers.
It would be nice if some ships could produce some units like Galleons in AoE3.
The low ship limits in AoE3 were not fun though but ships in the middle ages where historically smaller anyway so it would be more fitting to build some more.
Small and trivial thing that some units cost more than one population. In AoE1/2 elephants cost as much as infantry or villagers. Cavalry should be 2 and elephants or siege weapons around 5.
Ships (if they use the same limit) should be around 10.
Relics that have different modifiers like in AoM. In AoM relicts don’t just give you a bit of gold, they all have unique boni that might change your strategy a bit.
There are obviously things they shouldn’t keep from AoE3 but I’m not afraid that they will keep to many things from AoE3. No way there is going to be a 7 tower limit.
I assume that the defence (at last for most civs) will be much stronger.