so... you want a challenge, CTC? I'll give you a challenge.
Meloetta @ Assault Vest/Leftovers
Ability: Serene Grace
EVs: 120 Spd, everything else is up to you
Timid Nature
-Psyshock
-Focus Blast/Shadow Ball/Hyper Voice
-Calm Mind/Focus Blast/Shadow Ball/Hyper Voice
-Substitute/Focus Blast/Shadow Ball/Hyper Voice
Latias @ Life Orb
Ability: Levitate
EVs: 252 SpAtk, 4 SpDef, 252 Spd
Timid Nature
-Draco Meteor
-Defog
-Thunderbolt/Hidden Power Fighting
-Hidden Power Fighting/Healing wish
Meloetta is a more defensive version of M-Gard, sporting more physical bulk and pretty much matching M-Gard in SpDef, though this can be boosted by Assault Vest if you choose it. Latias is there as a lure and as a way to alleviate Meloetta's monstrous case of 4MSS, with HP Fighting OHKOing Bisharp and 2HKOing TTar, which really bother Meloetta. However, if you run Focus Blast and you don't think you need it, you can run the standard Healing Wish instead. Thunderbolt is to beat non-AV Azu, as well as having great coverage overall - I don't need Psyshock imo because Meloetta has it.
As you can see, I gave you a lot of room to work with, and that's because I gave you such a hard mon to build a team around. And I actually do have restrictions, but if they prove absolutely impossible to accomplish, you can break them.
1.) No gengar. Gengar is the only Pokemon I hate enough to refuse even using it.
2.) Display Meloetta's niche - don't use it as a lesser version of a mon just because I asked for it.
3.) If possible, try to make the team able to hold its own in a tour or the ladder.
4.) Did I already say no gengar?
Hopefully, this'll give you a proper challenge.