Don't take it the wrong way.. I think it is great to have such a service offered because it shows that BitSend get's serious attraction and such services are really needed..  but your conditions are not very appealing to me too in both points. The precentage (I prefer models based on the real vps costs + your service costs, fix costs ) and the initial payment frequency (I prefer upfront payment over several months because I am "lazzy" which of course is a bit troublesome if you want a precentage instead vps + service cost )
Just a feedback and yes for others your model might fit.