I don’t believe the once speculated MmewtwoY-EX/Lunala-GX combo works as (unknown at the time of original speculation) Lunala is a stage 2. Mmewtwo-EX generally doesn’t worry so much about matchups where it gets 2-3HKO’d; kind of the point in using shrine of memories.
So this leaves the choice of which you want to focus on: If you can’t get shaymin-EX, I suggest Lunala-GX, making the line thicker and abusing tech psychic basics like Gallade-EX, mew EVO, mewtwo EVO, mewtwo-EX, natu ROS, wobbuffet, Espeon-EX, (Espeon-GX may be a bit too cloggy) in combination with max potion (the age old combo). Do note [c] attackers can also be comboed with lunala-GX.
As for suggestions: Increase rare candy counts, N count, add max potion, maybe add a tech oranguru (has a usable attack), add 4 vs seeker (please), add 2 Lysandre, add 1-2 exp. share, increase cosmog to 4, cosmeom 2-3 copies, lunala GX 3-4 copies, swap mega turbo for 3-4 max elixir, swap 1-2 float stone for escape rope, swap shrine of memories for potentially a 2nd parallel city (want to cut off your opponent’s ability to dump shaymin-EX/hoopa-EX) note silent lab is an option, remove mewtwo lines, remove prof letters, remove bruxish (???Not sure why its in here???), remove DCE.
N.B. ultra ball is still good within a format containing nest ball (could add 1-2 of them ontop of ultra balls tho)
N.B. try out both 1 Ace Trainer and 1-2 acro bike if there is space leftover.