> Ex you have bxlgariia, bxlgarin and bxlgarski.
> Bxlgarin is bulgar-man, and -ski is only a suffix of adj., so one
> could loan "bxlgar" for "Bulgarian" (adj.) and have bxlgarxren and
> bxlgarxsek. Another loanword could be bxlgariia.

We should _most definitely not_ do it the Esperanto way (described in the
bottom half of http://www.xibalba.demon.co.uk/jbr/ranto/s.html). We should
do it the Chinese way: Bulgar-land, Bulgar-man, Bulgar-language...
completely regular and predictable.

This way you'd also avoid the question of why you took the masculine forms
(-in, -ski) when not only feminine (-ina, -ska) but even neuter ones
(*-ino, -sko) are available.

(And, actually, the Slavic -in- suffix is just another adjective-forming
suffix. It does not automatically refer to people.)