I think it is a good idea......need to twick a bit:
1) make it an online submission for the assentors and allow an anonymous result to the applicant with feedback. Sinkies (if allowed to remain anonymous) will be more "daring" to say NO to the bugger and give reasons. The applicant will also not be able to know who did not support but will be allowed to know why. The applicant will also need to be more careful in choosing his supporters.
2) Limit the assentors to 1 or 2 supports per year so the support is spread out amongst sinkies.
3) above (1) will also discourage "profit motive" support you can pay but you won't know if you benefit from the payment.