A few quickfire things before I go to bed, because I can just see this somehow getting out of hand because the terms "mobile armor" and "Dendobrium" were used:

Gaplant TR-5 can indeed serve as the core for a few attachments and separate machines, some minor some huge. In that sense it's similar to the Stamen mobile suit along with the vast majority of units from Advance of Zeta, because it loves that gimmick. Even with the Hrairoo upgrade is is still not a massive mobile armor frame mounting its own I-field unit and humongous weapon load, it is not, I repeat, akin to the Dendobrium in that regard. Stop panicking about the term "mobile armor".

I am not taking the Fiver or Fiver II which are legitimate area dominance machines. The Hrairoo parts can indeed mount Psycho Gundam arms on their multipurpose hardpoints, amongst a bunch of other stuff, but that's not the plan unless the GM decides to integrate this into a plot moment for some reason. Because where are you gonna find Psycho Gundam arms? It's just a Gaplant with enough weapons to not feel naked compared to advanced machines and to compensate for the fact that it won't carry handheld ones for stylistic reasons.