Yeah you'd need to update all the structs and opcodes to that code base. Huge amount of work. If they still use a titanium install might be able to find an archived version from titanium release date and save yourself some time.
My understanding is that the primary change that has to happen is to take into account the rotating encryption that P99 added.
Once you've done that, most of the rest of the work is done for you by SEQ from past work. Someone who was interested in that could just pcap a couple of sessions on P99 and use that to test so you're not having to test live.
Back in the day when I developed on showeq circa 2004 the rotating encryption required a closed source dll call libeq (I think) that provides the keys to decrypt. It wasn’t ever open sourced and I don’t know if it would be possible to decrypt the stream without it.
You’re better off trying to get myseq to work instead