I have wired up my last two aircraft using the built-in intercom function of the ICOM A-200. It works fine. I used two PTT micro-switches, plus a toggle switch between transmit and intercom functions on my first aircraft, and on the RV I added another toggle to switch between hot mike and cold mike, mainly so if I flew with a passenger that talked a lot or couldn't use the PTT intercom switch, I could set it so they could talk freely.
The wiring was challenging , at least for me, and my next aircraft will have a separate intercom unit for that reason.