The value of ZCP is definitely debatable. But if you were going to get EDC and 19" wheels anyway, then you're essentially only paying an extra $250 for adaptive EDC Sport mode, a different MDM calibration (though Euro MDM is better and can be coded onto either car), the suspension tweaks, and a different style of 19" wheels. I got EDC and the 220M 19" because I preferred the 220s to the 359s and didn't care about the rest of it.
Not sure what you mean about riding around in Sport but dialing everything else back to Medium -- what car are you talking about and what is "everything else"? But the M3 allows you to adjust throttle, suspension, steering weight, DSC, and (with DCT) shift speed all completely independently for M mode -- outside of M mode, you can set a default startup EDC and throttle setting, but you can't use MDM or Sport steering and on DCT I don't think you can set a default shift mode. Also, be aware that if you don't have iDrive, MDM is pretty much forced on in M mode -- so if like me you want to have lazy and spirited settings both for the road and thus keep DSC on in both cases (I use Euro MDM / DSC off only on the track), that won't be possible, though I suppose you could manually turn it back on with the button after toggling M mode on. But at least unlike the Z4, for example, you don't have to deal with sport throttle and shift speed if you only want sport suspension, for example.
Yes, if you remove Nav you remove iDrive. The X3, F30 3 Series, and some other newer BMWs do indeed have iDrive standard with only the navigation function optional, but that's not true of the M3. I really, REALLY like iDrive even though I seldom use the navigation function; it's just a great interface for infotainment management, configuring the car, monitoring status, etc.
What's the paint code you've selected?