I'm not sure where exactly you are picturing a transfer switch. Hybrid inverters have internal contactors to switch between passthrough modes.
I would personally install an interlock on the CLP with a separate feed direct from the grid main panel, so that the CLP can be manually failed over back to the grid if the inverter dies or while it's offline for troubleshooting and maintenance.
Basically, install the CLP like a regular subpanel from the main, with a main breaker on the CLP, then install a generator interlock kit on the CLP with a "generator" backfeed breaker. Then the inverter takes it's input from a load breaker on the main panel, and feeds it's output into the "generator" breaker of the CLP. Interlock should be cheaper than transfer switch, just make sure to buy a main breaker panel for the CLP.
You are allowed to buy say, a 100 amp main breaker panel and use that as your CLP, even if the feed from main panel to CLP is only say 60 amps. A 60 amp load breaker on the main panel will serve as OCP, and the 100 amp main breaker in the CLP will just serve as an interlock disconnect.