Actually, yes.
Sai created his Cursed Seals for a different reason than Orochimaru. A Cursed Seal, normally, is created in an attempt to control its target. Sai never let anyone know about that effect, which is how he killed his mentor, half-brother and best friend. The purpose of that was actually to keep them from abusing them, as during his initial creation of them, he was leery of just giving them away, and for good reason.
Sai made various Curse Seals, much like Orochimaru had various ones, but they all did have the same 'stages'; however, Sai's had a twist. Their Stage I release simply gave them a slight strength boost via nature chakra, as did the original seals, but their Stage II was different. Instead of giving them a complete Sage Transformation (although it could), it gave them one of two things: a weaker version of any Kekkei Genkai that Sai could recreate or a new chakra release. Sai could take the DNA of any person and create a weaker Kekkei Genkai from it. He did this with his extensive medical background and his personal Kekkei Genkai, which was the Jugo Clan Kekkei Genkai. Sai contained the DNA of Senju, Hyuga, Uchiha, Hon, Uzumaki and himself, thus could give seals for a weaker Mokuton, Sharingan, Byakugan, or simply empower them since the Uzumaki nor Hon had a Kekkei Genkai, thus only leaving the Jugo Clan Kekkei Genkai. Thus, the seals came in five possibilities: a weaker Sharingan, a weaker Byakugan, a brand new chakra element (no advanced natures), Mokuton (only advanced nature) or a full Sage Transformation. However, because they required at least a little DNA of Sai, each seal literally had a portion of his DNA in it. That is why purging those with the seal was so important.
Edit: Yes, Sai had several implanted Sharingan; he used them to control the five Bijuu in his body. No, he never had the Rinnegan and to the knowledge of this roleplay it has never exist. Neither has the Eternal Mangekyou Sharingan.