How will it effect the game?
-As long as 3.5e keeps the "on the back of a charging mount" vs. charging yourself distinction WRT lances, Rhino Hide, and Spirited Charge, it probably won't break anything except Rhino Hide armor. (And that won't be any more broken than it is already if only the first attack is interpreted as receiving the benefits of charging).
BTW, there is now a feat that does what a Rhino Hide armor does (i.e. double your damage on a charge).
This could cause a beefed up half-orc with 30+ strength getting an extra 40+ damage on a single hit (or 80+ damage with a critical) or much, much more, depending on the extra things (like shocking burst / thundering) on his weapon.
(how 30+ strength? For a 9th level half-orc BBN, Starting 20 + 2 ability points + bull's strength + righteous might + divine favor....)