Since converting a .deb file involves one Debian package that is not in the repo, Basically to use dependencies, I would simply import the dependency, or if it is multiple dependencies then use the file list option of sce-import. You can make a .dep file for your simgle converted debian package SCE, but entering both into sceboot.lst does the same.
I would rather not try to weave the conversion of one deb package into the sce-import routine. In the early days an SCE was simple and combining them was easy. Not so now and would not be feasible to try and combine the two. If one has a deb package that is useful but not offered in Debian but redistributable it could be put in the prebuilt section.