The problem with this kind of premine are forks and clones.

Don't get me wrong, I love the Idena idea and implementation, and I think devs should be paid. This is a work. And Idena is really original and is working now. It is not a concept.
But soon (when the alt community react to this great coin) I predict someone will fork the project with 0 premine. And this will be a challenge for Idena.

Other solution would be implementing a DAO with the nodes as a masternodes and some percentage of the reward of the blockchain for development. This would be the ideal solution IMO.