With talk of Star Trek: Strange New Worlds being in production and rumors of a return of the great Scott Bakula to a Trek franchise, the convenient idea would be to bring back Bakula as Jonathan Archer for the new series Strange New Worlds. Now the idea may seem far-fetched, but remember that Leonard McCoy appeared on both the Original Series and Next Generation as the same character, despite 71 years passing by between both franchises in canon.
Archer was, at best, in his late 40s when he took over command of the Enterprise, and since there were about 100-odd years between the events of Enterprise and Discovery (when Anson Mount debuted as Christopher Pike, the star of Strange New Worlds), Archer would be in his mid 140’s. McCoy was 137 when he retired from Star Fleet, so the notion that Archer would be dead just isn’t the case here. Modern medicine has clearly extended the quality of life for many.
You could also just do some type of James Kirk-esq scenario where Archer had gone missing shortly after the end of Enterprise, only for him to pop back up in the future. There’s really no canon on Archer beyond what we got in the show, so you can easily redirect his character into the future by saying he got worm-holed.
For T’Pol, it’s a lot easier to get her into the show. Spock was already 157 when his character left the prime timeline and traveled back in time to create the Kelvin timeline. Plus, Vulcans just live a crazy long period of time. So it wouldn’t be hard at all to create some type of workaround for both to still be kicking.
Or, again, time travel-nonsense.
Frankly what fans really want (or just me) is a fifth season of Enterprise. Bring back the whole crew, make the ending to the series non-canon, and just do more great work with those great actors.
If we can’t get a fifth season of Enterprise, then working as many as you can into Strange New Worlds is the way to go.