It’s probably not going to actually help.
Can you elaborate on why you think two pi’s would be better?
Mostly simplicity and the ability to use stock software and setups unmodified; also the likelihood that you’re going to find the dual concentrator gateway accomplishes nothing, so it will be easier to separate two already distinct gateways to two locations.
My concern was that two concentrators might saturate the SPI bus itself, I would have thought putting them on separate busses would address that fully.
I think that’s unlikely to be an issue, but I don’t disagree with using two busses if you have them in the sense of both hardware and understanding the needed software configuration support.
My main argument against the whole idea is complexity and lack of a likely benefit. At least, I’d try your ideas with two single-concentrator gateways before I worried about creating a dual-concentrator one.
a 2nd concentrator would allow us to use additional receive frequencies.
That’s complicated in that you’d either need the dual concentator everywhere or figure out how to command some but not all nodes to use the additional set of channels.