handicaps to give the AI a fair go-
1) Set the AI advantage to say 110% so he gets more toys.
2) Don't use ammo units, since he does not know how to use these. Or limit yourself to 1 or 2. (They
are charged as artillery units for arty overload nowadays in any case).
3) If there is a "killer unit" in a particular era, then deliberately avoid using these - like say ATGM in the 60s. At least, dont overload yourself with them.
4) Deliberately take "lesser" tanks, etc., like not taking TI sighted units when he doesn't have access to them e.g. NATO vs AI USSR in the later cold war era. Or in WW2 if Germany, try using the P4 as your main tank even if Tigers and Panthers are available. Or play as the side that does not have TI, versus someone that can have such (i.e. play as USSR V NATO in the 80s). Or you can deliberately play the "inferior" side - like one of the Arab sides in the Arab-Israeli wars.
I quite like playing as Jordanians in '68 with 90mm Pattons vs a 105mm equipped high experience AI enemy, you have to fight smart then!
.
I also like playing as a "secondary" WARPACT country with less access to the high end toys than the USSR in the time frame, having to rely on say the T-55 in the 70s again means having to think a bit. Cuba vs South Africa in the bush war of the late 70s and early 80s, especially if you limit your (non core) leg infantry to Angolan allies is another. Tanzania against Idi Amin's Uganda in 77-8 is yet another pairing I like - you'll meed to rely on your Scorpions, which are easy kills to the Ugandans there.