I think it should be a fixed $ amount. I think $4000-$5000 is a good range where spam is prevented and small projects could pay for it.
On another hand, a very simple solution is setting up a max. number of proposals per month, like 20. Then, if the room is full, you have to wait till any proposal closes its vote process.
Thoughts?
I think the biggest potential issue with this solution is that it opens up an attack vector (albeit an expensive one) to spam proposals, so no valid ones could get through.
In terms of potential solutions, a nice sophisticated one could be having a couple of "tiers" of additional governance layers as described in:
https://www.dash.org/forum/threads/additional-network-layers-and-governance-v3.19766/
The tiers could be 1)Full proposals 2)Pre-proposals 3)Sub-proposals
I see the third layer (small proposals) as being voted on like usual by the masternodes, but they would be "optional" to review, and there would be no 10% voting threshold (maybe a 1-2% threshold instead).
That way, any masternodes that have extra time and attention could look over some of the smaller (<10 dash or so) proposals without diverting time from reviewing the major proposals of the month.
If this tier has a much lower barrier to entry, and tons of proposals pour in, you could just view proposals by category (like on kickstarter) for whatever category interests you.
Plus there wouldn't be any issue with swamping out the major proposals with lots of tiny stuff, but you could still afford to properly review a lot of smaller projects.
Since that solution (and a lot of the more complex solutions) would require waiting on evolution anyway, I think any good interim solution will have to be very simple, such as a fund payed for by a normal proposal that just directly pays out to some of the smaller projects like DashForce does for meetups.
The fund could just be directly curated by a couple of trusted members of the community that have spare time to run the thing, and they could just provide a summary of what they are funding.
Crude, but I think it could work in the short term.