1.Stats: Should Mightyena get a stat boost, Evolution, Mega Evolution or nothing?
Mightyena can only really work with an evolution. It evolves way too early to get a significant boost beyond +35 BST.
Poochyena probably needs more boost than Mightyena though, as it doesn't reach even Zigzagoon's level.
2.Should Mightyena get more abilities?
Much like Manectric, its abilities are decent but too under specialized. Strong Jaw and Defiant would work really well.
3.Should Mightyena get more moves?
Obviously. Mightyena lacks powerful coverage options, but stuff like Psychic Fangs and Crush Claw would work.
4.What additional typing Mightyena can have?
Normal, Fire, Poison and Electric are the only options. Ground, Steel and Water can also be argued for.