I don’t think the part of Reina’s phrasing that Xanadu shares is the cause of that limit.
Reina says:
The rez cost of the first piece of ice rezzed each turn is increased by 1.
And the relevant UFAQ says:
Reina’s ability only lasts for the duration in which the Corp is paying to rez the ice.
But I think that limit is just how the “the first piece of ice rezzed each turn” part of Reina’s ability is implemented, and I don’t see any reason why it would apply to cards that increase rez cost more generally.
I think the RNG Key UFAQ ruling about Breaker Bay Grid is more relevant:
If a Runner with RNG Key runs on an R&D with Breaker Bay Grid rezzed in its root, what number does the Runner need to name in order to gain credits from accessing a Vanilla?
The Runner must name -5.
Xanadu’s phrasing is much closer to Breaker Bay Grid’s than to Reina’s, as it doesn’t mention an event that its cost change could be limited to.
I don’t think those are necessarily mutually exclusive, but I think you are both making a similar point. Usually it is a “type” of deck that hits T1 just based on playstyle vs. current meta. That said, I think playing both non-T1 decks and decks of a different play style (whether those overlap or not) is hugely valuable, as you learn a playstyle that has certain lines of play that cross-over between disparate decks situationally. For instance, when you decide to go “tag me” might have a lot of bearing on your experience with run econ/pressure decks and how they inform you on when servers are weak to that pressure. That’s valuable inference that you can learn by getting out of your comfort zone(if you haven’t played those decks before). Tying back to the original point, that might also be a T1.5 deck in the meta as it stands, which means y’all are basically talking about the same thing.
No, it’s perfectly legal.
Reina is telling “the first”, indicating a triggered, and Xanadu is constant.
Reina : "The rez cost of the first piece of ice rezzed each turn is increased by 1."
Xanadu : “The rez cost of all ice is increased by 1.”
Aghorra, for reference : “Break ice subroutine on a piece of ice that has a rez cost of 5 or greater.”.
Bastion : ice, rez cost 4c.
==>
you can’t break Bastion with Aghorra if you have Reina, because at the moment you would pay the 1c: break", this is past the “first piece of ice rezzed” point and Reina’s rez cost increase is no more in effect.
you can break Bastion with Aghorra if you have Xanadu, because at the moment you pay the 1c: break",
Xanadu’s rez cost increase is still in effect.
The same logic goes for the constant on Wormhole :
Wormhole (for the sake of exemple) : “ice, rez cost 9c, Wormhole can be advanced and its rez cost is lowered by 3 for each advancement token on it.”
you can break an unadvanced or 1x advanced Wormhole with Aghorra.
you can’t break a 2x advanced+ Wormhole with Aghorra.
Applying your logic for Reina / Aghorra on Xanadu / Aghorra would mean you can break 2x/3x adv Wormholes. This is not the case.