It seems that units that handle both IN and OUT are a rare breed (except possibly when you get to the really high end of the spectrum - a place I don’t inhabit!), so yes, if you want both autopilot and ADSB IN, then the iLevel might be a good choice, but it doesn’t replace your transponder. You still have to get a separate OUT unit. Given that you already have a transponder, you perhaps should just go with a Sky Echo for your ADSB? Alternatively, if you really want to upgrade your transponder, then getting an ADSB OUT equipped one will halve its price courtesy of the rebate. You still have to get an IN device though, which doesn’t attract the rebate (they don’t care if you can’t see others, they just want to make sure that others can see you).
As an aside, doesn’t the iLevel autopilot rely on adding extra trim tabs on the wings? Would that cause problems with your 24 reg? I haven’t looked at the iLevel lately, so perhaps it has changed.