If there is no OrgDb package for your non model organism, and you need one, then I guess you'd want to make one. Not clear to me why you'd want to put these annotations in a BSgenome data package. These packages are meant for the genome sequences. Could you clarify what you are trying to do? Also what kind of annotation you have access to for your non model organism? Note that if they are in a GTF or GFF file, you can import them as a TxDb object by just calling makeTxDbFromGFF() on the file.