Regarding Turnberry and possibly Troon the alternative on this one would be Prestwick maybe 2025 which means that it was 100 years since the last Prestwick Open. Like at North Berwick possibly take 15 and 18 out and build two longer holes north of the site like Adrian Stiff said a few years ago and finish on the 14th green. This would be like what USGA did with the 2013 Open by taking it to Merion.
There are other many courses on the Ayrshire coast but the question is are they a stern enough test.
Or R&A could go north to Embo, Royal Dornoch or Castle Stuart to boost the ecomony in Inverness
Alternatively maybe use Portmarnock even though Ireland is not part of the UK
Bingo maybe it is time to take it to Wales for the first time