"I" versus "we" in grant application
Your paragraph is less informative than, perhaps, it should be. If you give citations for each claim then it becomes clear. Give a reference after "previous work" and "paper Z", etc. Then the I and we is obvious.

I think that readers of a grant application will want those citations, actually. "What previous work...?" 

But an "Royal we" is often used as you say, but it would be a consistent usage. And it could sometimes be interpreted as "we = researchers in the field generally"