So the mass polymorph spells state that they're treated as the level 1-3 version of polymorph except for as noted above. Which basically means the cast time is longer and it hits multiple targets.
Now my question is what is the point of the mass polymorph spells? Since at the earliest level, level 10, you'd cast the spell and then destroy your party's ability to contribute to a lot of things meaningfully. For example, say you changed a creatures form and all its equipment melded into it, leaving it with a natural attack as per the level 1 polymorph, with a max of a +3 to hit for 1d4+3 damage...
I suppose an argument could be made that it's for the utility. And I guess you could use it to give your full party a swim speed of 20ft for 10 minutes... But that seems like a very trivial use at level 10. Other than that, I'm struggling to see the usefulness.
Or am I misreading the spell? And now the attack bonus would be equal to if you had cast level 4 polymorph, not great, but mostly functional then. And that'd scale any DC up quite a bit as well.
Has anyone used the spell? Is it's really just for utility? Or is it actually useful in other capacities?
You only lose your weapons if (1) you're holding them when you are polymorphed and (2) the spell changes your type. But you can set your weapon down and pick it up again if changed into a different type that still has hands.
Most importantly, you can just grant a polymorph form that doesn't change your type. Pick a humanoid form (which most but not all PC races are) and add on the abilities you want, that's what you use if you want to keep your equipment without any hassle.
For me, the most useful things to add to a polymorph form are racial abilities that you've dumpster dived from the PC races, plus maybe some resistances or senses (although there are usually racial traits that include a sense plus something else and are a better deal) and the free movement upgrade. I only like changing type if I'm trying to hide power armor or heavy armor, it's great for a technomancer who has the spell cache that allows a permanent polymorph effect.
Those are interesting ideas. Since the level 1 polymorph says you're still recognizable, does it still absorb your gear if you select a subtype different from your normal one?
I ask because I'm actually working on a technomancer in powered armor for our current campaign. And right now I'm trying to decide the best cache to use. The devastator seems to pair well with spellshot. The holographic artists is nice for the holographic image spammability, and the gene hacker would allow what you mention, permanently invisible powered armor. I'm just not sure what would be most useful since this is our first Starfinder game.
I suppose you could probably find a couple decent out of combat specific special abilities for the level 4 mass polymorph then though. And then with level 5 and 6 you can grant racial traits like the bane one to the whole party.