What would you most like to see in a RA2/YR mod? A record number of new units? New skirmish modes to add a unique twist to the game? New multiplayer or single-player maps, or a combination of all these? What's your opinion?

I would most like to see, a new BRAND NEW Yuri Campaign for singleplayer...

Good one! Not many mods have a full Yuri campaign. I don't even know a mod that has a Yuri mission in it!
I personally would like to see new campaigns for all 3 sides, about 50 new units, and skirmish modes that change those 50 units into another 50 new units that have different weapons and make you drop your jaw at the sight of all that replay value.