The Maps in aoe2 are allready including the random maps of aoe1. The only things currently missing in aoe2 are Gazelle (which would be a great addition to african maps) and Whale which could be included in Water maps.
Ruins and artifacts could be added just like Relics depending on the game mode.
Is there anything else that is missing on maps in aoe2 compared to aoe1?
Discoveries, although in AoE1 I think they only feature in one scenario in the tutorial campaign, and were mostly used for snow in custom scenarios.
There are a couple of random maps from AoE1 that are not in AoE2: Narrows and Hill Country. Arabia used to be pretty much the same as Hill Country, but it’s been changed so much with DE that it isn’t really the same anymore. (In fact, AoE1 and AoE2 handle random map generation quite differently, so strictly speaking none of the AoE1 random maps are in AoE2 – although I’m not sure how important that is.)
AoE1 had quite different resource distribution in its random maps, so that will probably have to be adjusted when playing Return of Rome – although I guess it depends how similar they keep it to AoE1.