>>36058977No Guard also means you'll be throwing out perfectly accurate Zap Cannons, which is just ridiculous.
Magic Bounce works but awkwardly ruins Starmie's niche as an offensive threat that spins hazards away on forced switches, and it's also awkwardly the fourth magic bounce mon.
I like Protean a lot on Starmie, because Starmie's impressive coverage (especially in the form of boltbeam) has always been one of its main draws. It just needs to have its stats toned down a bit.
HP: 60
Attack: 75 -> 85 (+10)
Defense: 85 -> 105 (+20)
Sp. Atk: 100 -> 130 (+30)
Sp. Def: 85 -> 105 (+20)
Speed: 115 -> 135 (+20)
With this it still outspeeds and OHKOs or 2HKOs most of the offensive meta, and it still has enough power to break through defensive cores. Now it needs to pick its coverage slightly more accordingly, and instead of just blitzing past every fast mon in the game, it has to keep an eye out for the usual suspects of speed creep. It has enough bulk that it can pull off its role as an offensive spinner, or it can just go all-out-attacker and break things apart in the early and mid game (potentially with recovery to make defensive switchins less of a threat).
Compare this Starmie to Lopunny and Manectric's megas. Lopunny has access to fake out and higher base power moves, and Manectric has access to Intimidate. Starmie blows both of them out of the water when it comes to coverage (effectively gaining stab on all moves it otherwise wouldn't), having perfect boltbeam coverage as well as high base power moves in the form of Hydro Pump and possibly Grass Knot, potentially pressuring offensive switchins with Scald, access to rapid spin, access to reliable recovery, higher overall bulk, the ability to remove its weakness to sucker punch/pursuit by using any non-psychic move... it's a pretty massive leap ahead of the other Pokemon around its speed and power tier.