Oops, I meant Tokiwa of Asama-class, not Asama. Tokiwa had been relegated to minelaying roles and sometimes escort duties before the war, and survived until 1945.
I think they can be sort of super escort. Slowness doesn't mean much for escorts, but being decently armored and having a big deck after removinng the old guns to mount all sort of things can be a boon. On the other hand, better engines would enable them to be ok-ish raiders.
I did the same with Tokiwa - went through my list of IJN ACs and just missed it. While super escort sounds sensible (Tokiwa even got some DCs in 1943), I'm not sure if (Tokiwa-asides) they were used for that (although could be wrong). Head's cracking at the moment though, won't try and think it out now. I think the stats should be easy enough (just base it on actual capabilities), but the trick will be in getting the AI not to do silly things with them (sending them up against modern CAs wouldn't have been nice!)