I'm a level 34 15/24 cav build and will have 8 riding soon. However, I want to state that even though I will be able to play my build, this is the worst fucking idea ever.
Can you fuck up everything I have special even more? I used to be one of the few agiwhores, now everyone is one. I used to be one of the few who will have 8 riding, now everybody who gets his hands on a respec or who gets to make a new cav char will have it too.
This is in no way a good or realistic solution to the problem of 'cav being OP', but you will probably increase STR requirements of heavy armour too so we will be seeing peasants on top of plated chargers and such. Cav might have been a little too strong, but I had to play HOURS to even be able to use my heavy horse for a few rounds.
Now we will have nothing but high agi cavalry, rather than the slower plated guys who could be easily stopped by pikers. Hell, why not just buff pikers to counter cavalry? I don't know how cav played these days, but I know the last time I played on a horse (before I sold my +3 heraldic barbed warhorse hoping zagibu would put in the heraldic heavy warhorse as promised), I got fucked up by archers in no time.
Yes cav was easy, but there are so much better ways to handle that problem...
QQ