i think i agree some formats could use filetype checks on upload, though w.r.t. your other point we have separate formats for famitracker modules (ftm, 0cc, and perhaps dn in the future)
that's really unfortunate, i'm sorry! i'll do a render for it if you want still (assuming it exports to nsf fine, which i imagine it will)
keep your eyes peeled for the allowed filetype extensions in the format description / lyceum article for the format in the future to hopefully avoid bummers like this : (