The T2 Chips are merely for Touch ID, Controller, and other Security things. macOS doesn’t run on it.Hardware limitations? Don't most of the newer 2018 Macs have T2 chips built in? I suppose the older ones could run in emulation mode but we don't know.
We don’t need additional hardware to run iOS apps on the Mac. All Apple needs to do is give developers the new UIKit Framework to make the Mac Counterparts (similar to the ‘Universal’ iPad/iPhone/Watch apps we have now).I've read that the MacBooks need Apple processors like in the iOS devices but I'm not sure anymore.