It's not an unreasonable question. Intuitively it feels like a WTO legal a quick fix that solves a lot of problems.
Unfortunately, it's not and it doesn't.
Well, let's say you start with a simple agreement that says all tariffs stay 0% both ways.
That's easy to write. @Lorand_Bartels famously threw it together over lunch.
... but as a government, you want more assurances.
So, you'll need to agree a TBT Chapter (like Chapter 4 of CETA).
Better negotiate an SPS Chapter (like Chapter 5 of CETA).
Should do a Trade Facilitation/Customs Chapter (like Chapter 6 of CETA).
A Subsidies Chapter is a must (like Chapter 7 of CETA).
You don't think so, which is why you're going to need Rules of Origin (like Protocol in Annex 30-D of CETA).
Why, whatever it says in the Dispute Settlement Chapter (like Chapter 29 of CETA).
Shit's hard, yo.
Tariff elimination would certainly help the select sectors like lamb and beef where the EU has tariff peaks, but proving compliance with an FTA actually takes MORE paperwork than just WTO tariffs.
The brilliant @AnnaJerzewska has written extensively on this.
It's not clear how much either side wants to begin contentious negotiations by putting all goods access on the table as a freebie.
This is probably why it's being pushed as a panacea by professional BBC news panel bores and not by trade policy professionals or the governments of either side. /end
Don't @ me trade nerds, it was already too a long thread.