Re: The optics don't look good
Remember that the current border is already a tax border and already suffers from a certain amount of smuggling and tax dodging
This is true of the border between any two EU member states where taxation levels differ between states; hence "booze cruises" where people go to Calais to stock up on cheap plonk because it doesn't have the £4 of taxes per bottle in France that it does in the UK, and people in Dublin driving North do do their weekly shop cheaper in NI.
This isn't really smuggling, because smuggling is normally considered to be the activity of crossig borders whilst avoiding customs, and there are no customs, because member states are in a customs union. There is smuggling into the EU (such as drugs being run into Eastern European countries from central Asia), and quite possibly smuggling out of the EU.
There are probably tax regulations involving buying goods in bulk in one country at one tax rate for resale in another (such as that bloke in the pub who wants tos ell you some Spanish tobacco). I haven't read up on such things, but I'd encourage you to do so if that interests you.
I can't see how a border-away-from-the-border could work. At some point, you need the infrastructure for checking. All this creates is a huge area between the actual border, and the infrastructure thet acts like one huge bonded warehouse. How would you manage this with the people who live and work at or near the border? What about those for whome the border runs through their house? Are they going to go through customs on the way to and from work in the morning? How far from the actual border are we talking? 100 yards? 1 mile? 20 miles? How many people will this affect? 100? 1,000? 100,000? What would the actual result be? We'd still have border infrastructure and even if somehow going by the letter of the GFA, it will be enough against the spirit to anger up the "new" IRA, UDF, et al who still exist, and I'm sure will be quite happy to switch back to terrorism alongisde their current occupation of organised crime.