I investigated Project Fi a bit, and quickly saw the issue with GV and the OBi. I have two accounts with GV numbers that I use - and don't want to lose those numbers nor the OBi connectivity.
I took the immediate step of applying for Project Fi with other Google accounts - ones where there is not a number I care about losing, or involvement of the OBi. One of the problems with the Project Fi beta is that you can't say "Thanks for the invite to my account "A", I want Project Fi, but I want it on account "B". You have to apply for an invite on account B.
I will be doing some in-depth investigation of options in the next few weeks - by mid November we need to either renew our two year contract at Verizon or lose the ability to keep unlimited data at the rate we are currently paying, and I need to see if it makes sense for some of us to leave because we don't use that much data. Project Fi looks interesting from the setup of the data plan - BUT I am very concerned about Google support of it as well as Google sticking with it - I have no desire to switch and then in 6 or 12 months have Google drop the plan and make my decision a bad one in hindsight. If I had to guess, I won't be going the Project Fi route, but that's what my research will confirm, or not.