Bhibb if you really wanna convert rpm packages to eopkg then,
1) you first convert rpm to deb using alien tool you mentioned.
2) Then convert deb to eopkg using either manual way for packaging solus packages as .deb acts as a zip file, or you can use the scripts provided by Solus 3rdParty repo, that repo also uses these tactics to convert deb to eopkg.
You can google / duck them if you want to know more about solus packages and solus 3rd party repo.