I don’t think that feats are a good long-term solution. Once you’ve blown through your feats, what then? Feats are only meant to be occasional rewards for milestones while leveling up, and stretch goals to guide progress. They aren’t intended to be a bulk source of xp.
I think the best way to raise xp for builders is to first identify actions that primarily dedicated builders do that non-builders typically do not. This is a bit problematic as boundless enables everybody to build freely as long as they have the required tools and blocks to do so. So, what do dedicated builders do that other professions do not?
Use of exotic and refined materials is a good place to look at raising xp values. Xp values of placing things like lanterns and refined gleam should be slightly buffed. Not by too much, since builders may tend to place hundreds or thousands of refined blocks that others may not bother with. Even a 20% boost to xp for these blocks would be a considerable boon.
Another option is to grant xp for prestige milestones reached. Builders frequently reach much higher prestige levels than somebody might reach just building their own utilitarian homes. Roads and large “public” buildings like the temple in Pixelgate or the numerous large portal hubs frequently top 300k prestige or more. Sizable scaling xp milestones every 50k seems appropriate.
Chiseling is an obvious place to raise xp rates. It seems to me that a 20% xp raise here would be good too.
I’m curious about how builders will utilize props like pillars and doors in their builds. Is it maybe worth it to restrict certain high tier props to just builders? Much like how craftsmen require skills to craft gem tools, and miners require mastery to utilize them properly, make builders utilize a skill to place progressively better props. Basic utilitarian props like shelves, tables, beds, basic wooden doors should remain free, exotic wooden and stone doors/poles and sone props are 1 skill point (sp), metal and gem props are 2, super exotic blink/ dark matter props (if they exist) are 3 sp. Then, add progressively better xp rewards for placing these items. A -xp gain for breaking these blocks prevents placement spam.
Lastly, how do we tie builders in to the contract system? Is it possible to make contracts track prestige gains made to another players beacon? The way I imagine this working in game would be a player (p1) contracting another player (p2) to build something inside of p1’s plots. Prestige gain or blocks placed could be counted until the contract is fulfilled. I don’t know enough about the planned contract system to expand much further on this idea.