This has all been argued before...
Justiciar is right in that a lot of people do have ambiguous "residence". And there is a strong correlation between pilots of upmarket aircraft and people with an ambiguous residence. Half the TBM/bizjet owners I see have a house in Jersey, etc.
So it is the low end of GA that is going to get caught up.
This cannot be what EASA intended, because - to the America haters in Brussels - the most provocative part of GA (turboprops and jets) will carry on as before. So why are they doing it? There is no possible honest policy behind this. It is like an income tax collection system where everybody whose taxable income is above £1M is exempt from paying income tax (they have that in Greece, I believe). This whole thing is the work of several powerful, crooked, dishonest and deceitful individuals running a private agenda within the EU machine.
As to actual enforcement, there is absolutely no reason to think that anybody on the ramp is going to give a flying **** about some pilot's residence any more than they currently give a flying **** about whether he carries an ADF and a DME, having landed off an IFR flight plan. In fact the pilot's residence is a good one level of abstraction removed from airspace requirements which are crystal clear, documented in every AIP, and have been crystal clear since Day 1 (decades).
If they ask you to sign a form saying you are non EU resident you just sign it... so what? The vast majority of the forms one has to sign at a big foreign airport, or when renting a car, etc, are unreadable anyway. Get yourself a mailbox in Jersey and use that address. The penalty is going to be zero because the advantage you obtained by doing that is zero.
The only thing driving compliance will be the tendency of pilots to self police, for insurance purposes. And that will be only for pilots who see themselves as clearly caught up in whatever the final wording is.
It took me 5 minutes to work out a perfectly effective way around the 2005 DfT reg on booting out an N-reg after 90 days' parking on UK soil. It took me a similar amount of time to work out a way for a suitably structured syndicate to do the same under the new regs. And there are far better brains than me out there.