I’m a fan of the idea of making adapters — we know many SLR camera bodies can take almost any brand SLR lens, with adapters made to fit between them:
https://www.google.com/search?q=camera+lens+body+adapters
And flashlights don’t need to autofocus and stop down iris diaphragms and such.
The “Yeah, but …” is the SLR camera lens mounts are expertly machined — known precision and repeatably. They truly are interchangeable parts.
Budget flashlights seem more variable even within any particular model or brand name — I’ve invited reports as people try Legoing parts
“What Legoes with What?”
But along that same line — any flashlights that are made accurately and repeatably within a model/brand would be ideal candidates for an adapter.