While I can see why you might want flash cannon (STAB..), it's really not that useful due to steel's poor attacking typing, especially on a magnezone, who really can't use steel STAB like scizor, metagross, and ferrothorn (on occasion) can use it. Instead, I'd recommend one of three changes:
1. Charge Beam- I guess it helps you out with setting up when you've trapped a choice banded scizor.
2. Mirror Coat- Strange? Sure. The feeling of laughing at a ferrothorn who gets sets up on because your opponent couldn't click anything else? Great.
3. Magnet rise- Unfortunately, modest nature magnezone usually means you're losing to the steel who would use earthquake (metagross), but if you can use magnet rise on a scizor, I guess it wouldn't hurt.... I'd recommend mirror coat out of these three, however.
And peaking of metagross, while garchomp can somewhat stop it, metagross with agility is a bit of a problem because STAB meteor mash gets a super effective hit on mamoswine (especially if it gets an attack raise, then shit's going down), and it will definitely leave a sting on haxorus, latios, and garchomp, and magnezone can't trap it effectively considering agiligross carries earthquake and will outspeed magnezone before you can ko it. Your only way of handling it is through politoed, and even then, considering you only see metagross on non-weather teams nowadays, you're hurting magnezone because hp fire is less effective. And even then, if metagross is packing thunderpunch.... uh oh.
Luckily for you, Metagross isn't seen as often these days, but this is something to keep in mind.
Anyways, great team you have here, and congrats on your success with it!