Yep, I didn't want to cram too many suggestions in one post, but I'm definitely in the camp of streamlining the system away from 3 currencies.
There should be an elegant solution around security, double voting, instant gratification expected from people who buy the currency wanting instant voting power etc. without the need for SP
Here though, I'm only focusing on getting rid of the 1.5% SP interest and using those funds elsewhere. Honestly anywhere would be less wasteful if people are not persuaded by what I suggested it should be used on, even just reducing the inflation rate by 15% would be better
Regarding just your proposal, I think it's a good one that makes more sense than keeping if for the reasons we currently are. I like your 5% number as well. The increase to rewards wouldn't be insignificant which seems to be a big growth driver...
The security could be addressed by holding the Steem in the "savings" portion of our wallets. It has a couple day window before it can be withdrawn which would give people some time to notice their wallet being hacked before it is too late.
yup there should be fairly elegant solutions
you can for example, even allow people to set the delay in the 'savings' vault
But I think the core issue is getting our incentives correct and a development fund is a step in the right direction. Hopefully development speed picks up as they feel more comfortable using their funds knowing the community is behind them.