I doubt the Romulans would make the kind of distinction you're making. The end result is that the ship is cloaked. Hence whatever technology is leading the ship to be cloaked is a de facto cloaking device.
Of course the Romulans would argue for as broad an interpretion of the treaty as possible. That doesn't mean their interpretation is controlling or, to the Federation, paramount. Your argument that a secondary effect is defining is not reasonable. I've given two very good examples of tech that might have that effect and that no sane person would consider a cloaking device. To advance the notion about warp 10+ tech or better ship materials would be disingenuous at best.
And here's another: the Iconian doors. Because you can get from point A to pojnt B without the Romulans knowing a thing about it. You've been effectively cloaked.
Does that really make sense to you? That if the Federation could master the tech of the Iconian doors, they would deny themselves that tech because the Romulans would object? Come, this is not reasonable.
And I don't see how phasing technology isn't, if not a weapon, at least a system with obvious potential for weaponization. You're making whatever's phased invulnerable to weapons. Unless the phasing technology somehow didn't also act as a cloaking technology, you've just created a technology that could be used in an obvious first-strike attack.
So? And the downside here is? The Treaty isn't a weapons ban or weapons development ban. It is specifically a cloaking ban. The Feds should be developing new weapons. The Borg are out there, the Dominion is out there, they better damn well be building some serious weaponry. Like maybe that soliton wave from New Ground. Whose primary purpose, by the way, was not weapon.
Impuise-only ships would be sitting ducks for warp-driven ships. But who would argue that warp drive's primary purpose is to be a weapon?
I would suggest that, at this point, the Romulans put their big boy pants on and develop better sensors.
Hell, it's Genesis all over again, where I respect the scientists' noble intentions but the potential for trouble is obvious.
Yep. Look where the wheel got us.
And Genesis can kiss my antimatter ass.
No, seriously, I'll sling some warp cores at worlds and you can keep Genesis.