You could do worse than post your API parts of the opening thread in the Tinkering Section.
It sounds like you know your way around a line of code.
For some of you other issues I think the answer is RAAT as suggested. Pi with HATS are the easiest and cheapest way to so this. Allo do some nice stuff, the allo digione may be a solution for your front room. As for the kitchen I have a Bluesound Pulse Flex and am very impressed. (The only thing lacking is a remote really but the buttons on top give access to main functions.)
The great thing about Roon is you can spend €100 or €10,000 on hardware and still enjoy the same experience. A worthy successor to LMS I feel.
.sjb