Syncing PortableApps

Hi guys. I'm gonna jump straight into this those please forgive me if I seem a little rude. Ok. I have 2 portable hard drives. I plan to have one permanently plugged into my pc and one take with me on the go. I am thinking of having all my apps and data on both so that I can simply sync them when need be. That way can do stuff at work, school and friends places, save it to my portable and bring it home and sync it to my pc using Toucan. What I need help with is the quetion of is there likely to be any posible issues that arise from this that anyone can point out to me.

Additionally I am thinking of setting my default browser and email client and music player and graphics editors and stuff to the apps I have on my portable that will be permanently plugged into the pc. I know this will create registry keys for the associations and what not but I think they will be minimal enough to accept. Now if I am syncing my portables back and forth will the default options travel with me? I want to be able to update my stuff from work and that but I dont want it so that my portable firefox starts acting like my default at work and stuff.

If any one can see any potential problems with this idea or has some suggestions to improve please let me know

Many thanks

EDIT: I'm not very good with terminology so if a moderator thinks they can title this post to make it better understood by readers please do so. Thanks.