@CplOReilly well said dood!
I totally feel the same way after thinking about it for sometime now. It makes so much sense to follow up in the series with a game to feature the last great empires of the world before the modern era. Like you said before ww2 wouldn’t make much sense because we already got the coh series, and other ww2 rts games that capture that era well. Big Coh and Coh 2 fan here , so as far as I’m concerned WW2 is already covered pretty close to perfect. Now WW1 has never been done in an RTS game to the detail level, say for example as in CoH2. Now that relic is on board makes me very excited that this might actually become a reality!
I imagine we could have the best parts of both series, Aoe and Coh, merged into one beautifully Epic RTS game. Ex: keep the unit discriptions like in CoH2 when you click on units thats adds that element of history and cool factor I always enjoyed from coh2
Keep it a base building/ army building game like in Aoe games. You could still have single worker units that gather and build, the more the merry 'R 
Have general’s that have different tech and abilities, as well as multiple nations for tons of varied strategy and play styles.
Have the UI from age games to display ur resources bUT also borrowing from COH a squad unit button selection style thing…the idea’s can go on and on if you just start to think of how both these games could merge into one.
Keep the map environment destruction from COH games , love seeing late game how the map has changed from being ravenged by war…
Keep the building like in Aoe games, anywhere baby you CAn build it anywhere!
I could Go on and on…
All that being said, WW1 would be a fantastic era to explore! There is so much potential for this game set in that time to become a classic…
I just picture starting off with a few citizens, having them collect different resources : wood, gold, food, ore, coal, oil. .etc ,have them build both economic and military structures, then teching up and unlocking steam powered unit’s or finally being able to use all that oil Ive been saving to finally start building tanks or planes.
Keep it at the heart an age game with resource gathering and building…
But focus micro strategy and combat as a CoH game and boy do we have potential!