I also wonder about the same thing. Further Pledge does not answer this particular desire of committing to a limited personal annual consumption while potentially saving for particular - or yet to be defined - causes later on. This can make sense also if one believes one's future view on what to donate towards being significantly more enlightened.

I could see such a pledge to not consume above X/year to be valued not overly much by third parties, as we cannot trust our future selves so much I guess, and even investing in own endeavors, even if officially EA, might at times be quite self-indulgent in some ways.

Still, I guess it would be possible to invest one's money into an EA-aligned fund that would later be able to disburse money only to aligned causes, incl. possibly your own project. That could provide some value in some situations.

Maybe it'd be easier, and worthwhile, to simply have an organization collecting pledges (and accompany one's verification of it) to not spend more than X/year; I think there might be a bunch of people interested in it.