Modern Vespa

So far, all good in the neighborhood with the engine. Still bedding in the rings, which is excruciating because I want to go fast! Question though: it's got a two-year-old stock clutch basket. Is this thing going to just straight-up open like a flower and frag the engine once I'm allowed to crank it to higher RPMs? Is that a thing that truly happens? Are those stock baskets with the band welded around them the best insurance policy?

You can weld ring on the basket. It will work. But better go to Cosa 2 type clutch.
Now at the top is VMC 10 Molle.

Cool! Dumb question, but do Cosa 2 type clutches accept the same clutch gear as standard clutches?

No. Gear is different. All clutch parts also different.

99% you also need to grind inside clutch cover and/or oil guide in the crank case.

Grinding I can do! So with a VMC clutch pack and one of these 23-tooth straight-cut clutch gears I should be good, then. I already have a 64-tooth primary gear installed from Malossi.

Buy this whole clutch and it will last forever. Cheap in the long run.
https://www.sip-scootershop.com/en/product/clutch-sip-cosa-2-race-ultrastrong-23-teeth-for-primary-64-teeth-for-vespa-125-vnb-ts-150-gl-super-180-200-rally-px80-200-pe-lusso-cosa-t5_93445300

Seems that VMC is better. With alloy basket it is also noticeably lighter.
Yes you need to use their steel plates, but on the other side steels stay much longer than on any other Cosa 2 clutch.
FMP have all answers in his videos.