Hey there, MacMaSt3r!
That's a really neat idea! I remember the days of previous Generations without the usage of Megas at all! It gained Fairy secondary typing, which helped it out immensely! But now that it is banned, it is harder to use Mawile because of its lower defenses and slow speed.
For your AV set: This seems like a good idea, and it surprisingly could work. However, I feel as if Assault Vest is only suitable for certain Pokemon. For example, Pokemon like Slowking are more viable because they have some sort of reliable recovery and can tank hits with their good defenses. Druddigon, Conkeldurr, Escavalier, and Goodra also are good candidates because they hit widely in terms of coverage and can tank hits as well. In Mawile's case, it's harder for her to tank hits because of her lower stats in HP and Special Defense. However, there could absolutely be a viable set that you could pioneer with! Just a little fixing on the EVs: Try
172 HP/ 252 Atk/ 84 Spe/SpDef or
248 HP/ 16 Atk/ 244 SpDef. Both of these sets allow for serious tanking of specially offensive moves and allow for decent Attack to dish out moves.
Though Sheer Force is a great ability, Mawile finds much more comfort in Intimidate and Hyper Cutter. It may not seem obvious but Intimidate helps Mawile face Ground and Fire attacks that would otherwise put her in a casket. Hyper Cutter also is quite useful against Intimidate Pokemon that would otherwise wall her until her demise. Sheer Force is quite practical, as it can boost up three of the four moves in the set you provided. However, Mawile is precious and delicate, and her abilities have helped her longevity out a bit more and could certainly help in the long run.
There are several sets that a Mawile could run effectively in today's metagame that would help out your team.
SubPunch set (Can get behind a Substitute and dish out Focus Punches and STAB moves to deal serious damage to opponents)
Mawile @ Life Orb/Leftovers
Ability: Intimidate/Hyper Cutter
EVs: 172 HP / 252 Atk / 84 SpD
Adamant Nature
- Substitute
- Focus Punch
- Sucker Punch
- Play Rough
Swords Dance set (Good sweeper as long as you time her appearance right, she can deal serious damage to most opposing Pokemon with her coverage)
Mawile @ Life Orb
Ability: Intimidate/Hyper Cutter
EVs: 132 HP / 252 Atk / 124 Spe
Adamant Nature
- Swords Dance
- Play Rough
- Sucker Punch
- Iron Head/Knock Off
And finally, a rare but sometimes effective one, the Resttalk set (Allows for Mawile to continue to attack opponents while Resting off damage taken already)
Mawile @ Leftovers
Ability: Intimidate/Hyper Cutter
EVs: 248 HP / 252 Def / 8 SpDef or Atk
Impish Nature
- Rest
- Sleep Talk
- Play Rough
- Foul Play
Those are all of the sets that would highlight Mawile's viability best. Good luck using her in your battles!
Hey! Thanks for your input and I will definitely try some of these out on Showdown to see if any of the mare viable enough to run.