Well I've done it. I've successfully integrated the Colubris CN-3200 series access controller into my hotspot scripty thingy. The MSC-3200 'should' work too... I'll test that soon.
The hardest part was trying to decide on where to set the access controller type. I could have set in in the NAS table in the database which would make sense but that would mean doing something on the server side whenever you installed one of these things. So I did it on the other end. On the access controller you simply pass 'nas_brand=mikrotik/colubris' back with the rest of the user authen data. My scripts read that and tweak things in the background to suit.
The tweaks are mainly what to set in the database for the radius reply for that user and the slight modifications of the template files with the differences in login forms. I think I must have done something right for the start because doing this wasn't difficult at all.
Now I just have document the changes, make a pretty howto (not much to do there) and create suitable location content that reflects the corporate identity of accessEzy.