While Freeze is a pretty great technology, expecting that it will solve all of your collaboration woes will lead to disappointment. My experience is that as Sets get large and complex, it gets easy to accidentally miss a track that needs to be frozen before you hand it off.
A few thoughts to help improve your workflow:
1) Freeze early and often. As you work your way through a track, freeze as you go. This approach has the added bonus of helping you commit to various ideas as you work. If it sounds good, freeze it and move on to something else.
2) Even better, treat softsynths as if they were hardware. One of the huge advantages of older hardware synths is that you get a sound you like, play a part and record it as audio. This limits your options down the line and keeps your production process moving forward. You can do the same thing with software instruments. Get a sound, create a part, freeze it, flatten it, move on. Done.
3) If there’s someone you’re really serious about collaborating with, a bandmate as it were, you should seriously consider investing in a common set of tools. Find a small set of plug-ins that you both like, and rely on them heavily. (Again, this has the added bonus of limiting your options a bit.) When you use other plug-ins, treat them as if they were hardware. (See above).