I've owned an L5000, L2500, and currently an L1505 but have not played the L5500.
IMHO the L2500 is the best one, but all three that I have played are good. I'm guessing that the L5500 is the same as an older L2500 just with the different pickups and preamp (EMG). I'd love to own one of each
And yes, I saw a 5 string ASAT posted here or the other place but I think it was a custom job not regular production.
As far as custom models and rare birds, maybe some of the more knowledgable folks will chime in.