Hello first post for me. I just purchased an M10/45 and very glad I did, it seems there is a lot going on with this platform in the recent months, all very exciting. I tried reading as much I could in a day having fresh eyes on this long thread.
I too would love to get a belt fed and magazine fed rifle firing upper. I was also happy to see someone suggested for a later project a 12/20g shotgun upper. What I am surprised about, unless I am missing something with the design, please let me know if I am, is that no one suggested a modular feeding system like the HK 21/22/23 to be able to feed different types of calibers from magazine or belts depending on what is installed. I know that this will increase the cost, but if it could function properly, might lower the overall cost as a single upper to build off of.