Suggestion: since you're incorporating mining but not using it to confirm transactions, why not just use BOINC?  (http://boinc.berkeley.edu/ -- grid computing for scientific problems, cancer, AIDS, protein folding, etc.) Benefits:

1. Ripple's already doing this, with their World Community Grid "giveaway", and it seems like as good a proof of work scheme as anything else.

2. It's doing something that is obviously good and useful with your computing power.  Might help you raise interest in Splash -- BOINC is useful in a much more concrete way than, say, finding long prime number chains.

3. It's easy for people to set up BOINC.  It has a user-friendly interface.  It runs on everything -- heck, I have it cranking away on my phone, because why not?  Contrast this with, say, cgminer or cudaminer, which are a nightmare to set up the first time you do it.