I think it's a great project (in theory), though there's some technical information missing from the proposal. I've pointed out a few gaps/questions that would need to be addressed, but in general I'm not sure if my tone should be kind of advocate/letter of ref (since I think it's an important study), or criticism/impartial evaluation (more like journal review?).
A lot of grants lack the specific details. If you think the grant should get funded, then tie the flaws back to the strengths. You also might ask a senoir scientist familiar with these types of reviews that is not part of the grant.