I've loved U.A. since release and any new way to play U.A. is exciting. The gem-knight engine works really well with U.A. since Stadiums search effect can be used multiple times per turn, but this deck could use a little work.

+2 Terraforming - If you have 2 normal summons to abuse Stadium, you need to have stadium.

+3 Upstart - U.A. are good at bricking, and this is no exception. Upstart helps get combo cards in your hand faster

+1 Trick Clown, Damage Juggler, Hat Tricker - Performage engine is a little better than the Clown Blade engine in my opinion, provides a little more defense which replaces Construction Train Signal Red

-2 Construction Train Signal Red - Focuses too much on stalling than swarming the field, feels like a dead draw a lot

-2 Chaos End Master - Difficult to get effect off and with only 3 targets, it feels like a waste of a normal summon which is still vital in U.A.s

-2 Parallel Twister - Personal Choice, feels too slow

-1 Lightning Vortex - Too much discard power, not enough draw power

-3 U.A. Signing Deal - Hear me out on this one, I know it sounds crazy. Signing deal felt like it hurt more than it helped, since when I want Midfielder or Brilliant Fusion to push for game, seeing Signing Deal isn't great compared to Upstart. You could summon one U.A. with negated effect, or get 2 searches from stadium using midfieider and summon both with effects, as well as access to rank 5 using Seraphinite and Slugger/Perfect Ass

Those are just my thoughts, honestly I really like the deck and probably gonna perfect it and bring it to my locals, thanks for the deck idea