Let's make a Trip Monkey Barbarian shall we ? We kick off with STR 18, we get the +2 racial, +4 from leveling, +6 from the belt, STR 30 @ lvl 17, raging STR 36, Improved Trip and Greater Trip. CMB when trippin' = 34...
We trip ze Cornugon at 9+, without any buffs.
There, done.
This comment pretty much destroyed the OP's argument. I"m still laughing over people actually complaining that their character can't trip a storm giant. Our characters are supposed to by heroes not demi-gods like Hercules and.....Drizzt LOL.
Fundamentally we don't want melee-types Tripping because... why? Because Tripping means they're demigods?