First, some background, provided by Memory Alpha. It's not complete, but it's a start. Then:
1. Worf's shoulder-cannon thingy from Insurrection fired some weird pinkish-purplish pulse. It's commonly thought to be the isomagnetic disintegrator, but it is my belief that it is in fact the tetryon pulse launcher.
2. The tetryon plasma from the USS Yellowstone was purplish, IIRC.
((What color were other examples of tetryon whatzits in Trek? It might help confirm or deny the idea that his shoulder cannon was the tetryon pulse launcher, and thus intended to knock out the Son'a weapons (a la Dax in "Blood Oath").))
3. Romulan cloaks of the 24th Century make use of a "tetryon compositor". When sabotaged by a Canadian, it can disable the entire cloaking system ("The Die is Cast"[DSN3]). Tetryon emissions can be detected from Romulan warbirds ("Visionary"[DSN3])
4. Could the tetryon issue be the reason weapons still can't be fired while cloaked? After all, if tetryonic things are afoot, the ship's weapons might themselves be impossible to use. Perhaps there is some sort of field effect in play, or perhaps the ship's plasma energy system gets tetryon doodads in it, or what-have-you.
4a. Obviously the ship shouldn't be flooded with high levels of tetryon particle radiation, since "Workforce"[VOY6] features the ship striking a subspace mine and being flooded by tetryons, poisoning the crew. While there may be an acceptable tetryon radiation limit in the Romulan fleet, I can't imagine it's a good idea. Then again, too much of anything can poison you, so perhaps tetryons are considered safe at normal levels.
5. In any case, one would have to figure out why hand weapons can still be used. I don't know about phasers, but I'm pretty sure that the Romulan who took Troi in "Face of the Enemy"[TNG6] was vaped by a Romulan disruptor while the ship was cloaked, and there may be other examples I'm not remembering which feature particle weapons fire on cloaked ships.
Suffice it to say that it's an interesting line of reasoning, but I'm not sure what can be done with it. I doubt we know enough about most of the subjects to come up with anything firm. Nonetheless, I might find something that helps in regards to offering more proof that Worf was using the TPL.