No doubt you are right, but there are also further things to consider.
- The Swiss/EU bilateral allows contractors from the EU to quote on Swiss government contracts etc... but they must use goods sourced from within the EU (not necessarily manufactured in the EU) and maintenance must be done under the same conditions. That means anything that was sourced in the UK, must now be sourced via NI.
- As for tourism, you may not know this, but European ID cards are no longer accepted for entry into the UK and EU/EEA/CH resident third country nationals now require both a passport and a visa. So mainland Europeans now need to go through all this hassle to visit one country in Europe. The three secondary schools in my town here in Switzerland used to organise trip once or twice a year to the UK in the past, but for next year, conditions allowing, they are planning to go to Ireland instead (teachers have contact me about it). The main reasons are the extra requirements - all Swiss students would have to get passports and third country nationals would have to get passports and visas, which represents a lot of extra paper work and expense.
I travel on a Swiss national ID card, rather than an Irish or Swiss passport because it takes about 15 minutes at the local community office to renew it once every ten years. We used to pop over to London for a weekend every so often, but we won't be doing this again in a hurry because of the extra hassle - it's Paris or Vienna from now on.