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Imagine an inverted Technician for Scizor.
Instead of weaker PP moves getting boosted by 50%, all STAB moves get a 50% boost.
Basically, unless I'm misunderstanding, Mega Beedrill may potentially have the hardest hitting U-Turn in the game. He gets Knock Off from previous gens too. Those two things combined are bread and butter.
While Bug doesn't have the best coverage, Poison is quite amazing, You just need something for Steel types in your arsenal (probably Drill Run) and Knock Off takes care of shit like Gengar that would resist both STAB moves.
Everything beyond this is speculation.
If he gets good or even decent SPA, he could run a mixed set using shit like Silver Wind (I know you nerds like gimmicks) and a small host of other special moves, including but not limited to hidden power. Beedrill might've been UU in XY had his stats been a bit better (Scope Lens-Sniper, while gimmicky, is pretty powerful with minor setup). Imagine what he could potentially be like with some stat padding in the right areas. If he gets the same treatment as most of XY's Megas, look out Scizor, there's a new bug in town.