I think the right choice is the one that makes JR to commit 100% of his time to the project. You can bet that competition will commit full resources of their founders to their project.
Half-measures are not good for such a project. If the "buy back" is needed for JR to go "all-in" in MSC, then I strongly vote for the buy back.
Many people have said that they think it is imperative for JR to be on the project full-time, yet I have not seen anyone provide a reason as to why his full-time commitment to Mastercoin is necessary. Presumably the community feels that since JR conceived Mastercoin it follows that its development is dependent on him. But it's one thing to conceive an idea and it's another thing to develop it. Does anyone have reason to believe the JR would be such an exceptionally good developer?
I find the community's attitude towards JR untenable, and I partially blame JR for not being more direct with the community: either he believes his full-time help is necessary for the development of Mastercoin, in which case, if the community and the board agree, we should do what we can to get him on board full-time. If on the other hand JR doesn't think his full-time commitment to Mastercoin is necessary for development, he ought to say so explicitly, that way we can stop focusing on how to get him to commit to the project, and start focusing on the project itself!
In my opinion, JR obviously doesn't think his full-time commitment to the project is necessary for its success, otherwise, he wouldn't have published his white paper without any code, and wouldn't have explicitly said that for two years he tried to convince someone else to undertake this project.
He is the brain and soul of the project - additionally, he is also the major holder of MSC. It's clear as water that he has much more incentives than any "for hire" developer to make MSC to succeed. Still, there are real-life concerns that might refrain him for quitting his well-paid job to commit to such a venture as MSC. IMO we should just work for him to commit.
I honestly don't see why you are so certain JR is the "brain and soul of the project". Mastercoin was his idea, but it doesn't follow that his full-time commitment is necessary for its success. There are similar projects to Mastercoin in which JR is not involved, which should be evidence enough that the idea can be executed without his full-time help.
Also, it is by no means the case that JR has more incentives than a "for hire" developer to make Mastercoin succeed. JR has a well-paid job, and he has said that his wife doesn't consider any money that is not in their bank account real. A "for hire" developer, whose livelihood depended directly on the success of Mastercoin, however, would be highly incentivized to do a good job.