Anybody think a tweaked out 125 for extreme top end power could beat a stock 250 out of the gate? not really sure y this matters at all, but just wondering

No (simple question, simple answer).

...unless James Stewart is the pilot!

Okay, if you get Stewart then I want Ricky C on the 250. Rider ability changes the equation around, but if you're talking just the bikes and the typical rider, then it's still the 250. Or throw in another variable: how far to the first turn? I once rode a mx where the first turn was less than a 100 feet from the start line. Here, a good 125 and a hyperactive teenager could probably beat a 250 to the turn at least some of the time. Another variable: available traction.