I'd liek the ability to change Prof. part way through. But in order to prevent people becomin really unber i have some ideas on power checks.
1. Make it only possable when you reach a new title lvl. and you could only change Prof. ONE time, so you culdn't go back to your old, or another prof. later.
2. Make it cost a set amount of IP dependant on the TL (so you will have to save IP if you want to change thus gimping your self part way)
3. Once changed you can use no new nano's for old prof. only the nano's you have. And you can only get nano's for new prof that are same or higher QL as your LvL at the time of change.
4. Profession specfic "perks" for the old prof. would not be usable. Such as NS, GA, Prof. Quest rewards. and so on. But you would be able to get any such rewards that are in your new profession.
5. IP usage req.s (the colors) would change to match the new Prof. and so you arnt totally gimped you would get a total ip reset to match the new profession.
Well this is just an idea and i tried to think about making it realistic and preventing really uber people from occuring. If you have any CONSTRUCTIVE idea pleae post or any bad side effects i might have missed too.