Of course she can be integrated. Take my idea of the argument, for example. You're changing only a bit of Yen's and Geralt's dialogue, inserting new dialogue from Triss. The character can be placed there and build her in to the cut scene by changing the camera angles so they focus on her as well. It's a relatively easy thing and far, far harder things have been achieved by your average Modder for Skyrim. That game doesn't even have cut scenes and modders have created them from scratch so I'm sure a company of the standard of CDPR could, with the will, integrate her.
Even if she didn't figure there, there's absolutely no reason in the world why she can't be in her own place doing her own thing for Yen with dialogue of her own. Again, beyond the acting, anyone with a modicum of modding experience could achieve this, so don't tell me a professional developer couldn't. It is the easiest thing in the world to integrate Triss in Act 2.
Again, the drinking scene, simply needs more dialogue with characters talking to Triss. It's not complicated. You place the model, give it the appropriate animations, and Bob's your Uncle, you've got her integrated. I'm no modder and I've been able to create new characters with their own routines using Bethesda's Creation Kit so there is no reason to assume it's complicated for a professional developer with professional development tools,. If they refuse to do this then it's not because it's expensive or because it's complicated, it's because they can't be arsed.
But like I said, I'll wait for official announcements and not someone's data mining who didn't even compare against the original release so you're all basing your assumptions of the changes on the most tenuous of information.
Personally think you'd have to remove dialogues like those with Eskel(where they discuss her absence) & later lambert(who teases Geralt about how is Triss) which wouldn't make any sense with Triss present. While i would have preferred a version of Kaer Morhen built around both women's presence, i certainly wouldn't want her added in if she wasn't integrated fully with the goings on. If she was integrated it would require tweaking multiple dialogues all the way through which isn't something i see them doing. It's much simpler to explain her absence & allow player ability to assert the romantic choice at this stage imo. I'm also taking these data minings with a pinch of salt till we have firm official details.