Can a theoretical proof-of-concept be published?
From your description ("I have done a bit of math, and it seems to check out"), it sounds like you have ended up in an entirely ordinary and reasonable piece of theoretical/analytical research.  Indeed, such research can be almost precisely characterized (informally) as doing a bit of math and seeing if it checks out.

The question of publishability then boils down to whether your simplifying assumptions are considered reasonable (which you can argue and test by comparison with prior work, both theoretical and experimental) and whether the conclusions reached by checking it out are interesting and significant.

Bottom line: go forth and publish (in an appropriately scoped venue)!