Transfer switch / sub-panel some distance from main panel
Looking for feedback on soundness of this...
The main panel is currently in one corner of the basement, obviously where the line comes in, in what is currently my workshop. This corner has become the unofficial wiring closet for everything from TV cabling distribution to Cat6 Ether. Combine the fact that this room may turn into a "den" at some point, as well as my desire to add a backup generator, something has to change.
I'd like to add a transfer switch / subpanel to a more centrally-located room that already contains the HVAC and water heater. This room, about 30' from the main panel, is also very close to the pellet stove, and the kitchen fridge is practically right above. By putting the transfer switch / subpanel in there, I could hook up all of the things I would want to run from the generator during a loss of grid power. I'm considering a generator in the 10-14kW range.
So, I'm looking at two thick lines from that corner of the house to the subpanel, one from the main panel and one from the backup generator that will be located just outside that corner. I'm thinking 6/3 (copper) and a 60A subpanel as a bare minimum, but depending upon the actual needs of the combined items (the HVAC's two-stage emergency heater is a beefy unit, around 3kW itself... this was installed before the pellet stove and is probably no longer necessary) may go as high as a 2/3 and a 100A subpanel. This is all off of a 200A main panel.
So, am I missing something important, like some code that says the transfer switch needs to be within so many feet of the main panel? Am I silly in thinking two runs of thick copper from that corner of the house is a good idea, even though it probably kills a number of future upgrade birds with one stone? I'm estimating about $2/ft for the copper, so $100-150 for that piece of the puzzle isn't bad compared to the multi-$k price of the generator.