Thanks to frostryder12 for suggesting this mega.

Mega breloom would keep its hidden ability upon mega evolving, technician, to boost moves like Mach punch. it keeps its typing and gets large boosts to its attack and speed. With these buffs Breloom would hit like a truck and be able to outspeed even pokemon like greninja, its attack stat resting at 170 a and its speed resting at 130. Its appearance changes to where it is now faster. Its tail gets numerous tufts of grass on it and the mushroom on its head gets more streamlined as does the rest of its body. It gets more powerful arms and legs too.
Stat boosts:
40 attack
60 speed