Do you have a good example of a proposal for development with a good detailed budget you appreciate?

As for the idea of the marketplace...
One way of looking at it is that we are in fact usually the very top marketplace in splinterlands that is used for buying cards, renting (and usually just a close 2nd for non card asset purchases). We are the only place you can do a whole lot of things and often many things are requests by the splinterlands team. One primary motivator of this particular proposal was someone on the team that petitioned us... one argument is that us developing a lot of these things has saved splinterlands team a lot of funds.