Sorry, but in my opinion your first 2 ideas are really no good.
Drasticly reduced times only for lower ages? While my sa base takes 14 days just to get rid of a piece of forest? No way....either reduce them overall or stay away of reductions...
It even frustrates me already that my sons ea base gets the same speedup bonusses as my sa age own base, which is ridicolous, cause 1 hour reduction on his base equals about 4 hours of reduction on my base...ad ergo, his bonusses are in fact way higher!
Rushed sa offensive bases can dominate non rushed sa defensive bases? No they cannot....i have an rushed sa offensive base BUT rushing means making choices... i always rushed to get my regurlar armies done and generals and selective factory troops.
In cw and sa i found out i totally rushed the wrong troops, cause barrack troops are not what you use in cw or sa...so i have been upgrading my ass off in sa for months to upgrade the right troops and stuff all the way from ia age till sa age....
What i am saying is: its all in the game and if an rushed sa base can kill an non rushed sa base, then that non rushed base must have done something thats not right! You can defend perfectly against an offensive base if you upgraded the right defenses!