Any open blockchain is a "public good" that needs to have a disciplined, transparent and systematic structure for supporting it -- or the investment which has been made in it's initial construction will obsolete or erode over time -- and the capital can't be an endowment, but should come as a flow of funds. This is really for psychological reasons, people twist themselves into all kinds of odd logics around spending from the income vs corpus of an endowment and expected future returns etc, so it's best to not even go there.
Not sure what the exact numbers are but at about 11 mm coins out and a 42 mm cap, the rough math would be that you'd be allocating 3.1 mm coins to the Dev Fund over the inflationary period of the currency. The interesting issue is if an allocation to the dev fund can help differentiate the currency by creating a well funded mechanism for development of the platform.
The trick there is that I think then the dev fund allocations/spending needs to be open to throne votes - or some sort of allocation process determined by the community, which might not be implemented initially for strategic/technical reasons -- but would be implemented at block X, or say when around 22 mm coins were out. In this way allocating 10% of the block reward to dev would involve allocating 1 mm coins to the discretion of the existing dev team and then 2 mm coins to the discretion of the community which is built around the network.
Just an idea... and worth keeping in mind that my thought on ideas is that the key to having good ideas is to have lots of ideas and listen to the feedback you get on them and keep iterating....
The counter argument to this is the fact that a centrally controlled dev fund is opposed to the decentralisation ideal. Having said that, the name Crowncoin implies a monarchy and autocratic head of state
You mention Throne votes, does that mean you are familiar with DASH? Their decentralised governance mechanism was implemented at about the same time I left their team.
We are planning on uplifting the Crowncoin Throne code to use the latest DASH masternode code in the near future but we haven't decided whether we will be using their governance model. This is something that we need to discuss further as a community.
We also have half an eye on what form DASH Evolution will take. Some of the Crowncoin team had input into that project, it will be interesting to see how it is implemented.