In a perfect world, I would happily devote more time to Mastercoin, I've lived and breathed it pretty much whenever I'm not working my day job & am of course 100% behind it - there is however an issue I haven't seen discussed which for me at least is significant.
There are real-world financial burdens (mortgage, bills etc) that have to be paid. My full time earnings are in fiat - and that's a critical factor. Cryptocurrencies are still a very new and volatile way of transferring monetary value (for example I had a fairly substantial bitcoin transaction earlier this week that was worth significantly less to the recipient in the time it took to confirm it in 6 blocks). Consider if you will, being paid in bitcoin & mastercoin only for the next {x months/years}. The ups and downs of these values will determine the amount of fiat you would have that month to pay the bills. It could be fantastic and you become very wealthy. It could also end in tears if a crash in value restricts your ability to pay said bills. My number one priority over anything else will always be providing for my family (and stably).
The foundation I'm sure would look at adjusting payments along with market values but just as volatility affects conversion to fiat, so does it affect the resources of the foundation. A crash in bitcoin value is also a crash in foundation resources. For the sake of debate, what happens if bitcoin for example crashes to $50? How would the foundation cover it's payments to its hires? I think that's an unlikely scenario, but unlikely enough to put 100% of your income on is the question. My apologies if this comes across as negativity that's not my intention at all - I'm simply considering (out loud) the potential risks.
Mastercoin is a project I thoroughly support and believe is going to be something that really starts to attract 'big money' (corporate) to cryptocurrencies. I currently spend as much time developing as I can, but I have a full time job which takes up the lion's share of my time. I still do endeavor to be responsive to any issues with any of my Masterchest software.
As they say 'never close a door' & I'm not ruling anything out, but as nice (I'm guilty too) as it is to get swept up in the incredible growth in just our first few short months when it comes to things like employment and where your income comes from (and how reliable that income is) a longer term perspective is needed.
Thanks

Note, I'd be happy to read any info anyone can provide on a precedent for full-time work paid in cryptocurrencies.
EDIT: for clarity
The Mastercoin Foundation has 4,500 BTC. At the current market rate that's almost $4 million dollars. The Foundation could sell some BTCs and pay guaranteed, decent (but not outrageous) salaries in fiat currency on long term contracts for select lead developers. As a bonus, MSCs could be rewarded according to amount of time employed or milestones achieved for potential massive upside and motivation of the developers.