But what is their real/more likely opponent? Pirates or an AFFS invasion?
Again, it depends on the era. We have three separate eras to consider.
1. In canon-3025, Thomas Calderon is not about to let the focus drift away from the FS...which would indicate that the TDF is using the wrong model. However, I noted from his bio that Thomas doesn't have any real military experience, and I think it likely that he decided not to tinker with something that seems to work well - 'If it ain't broke, don't fix it.'
2. #1 would indicate that the TDF has been configured as an anti-piracy force -- which makes perfect sense, given their location and position. In the aftermath of SW1 & SW2, I'm sure that there was a massive upswing in piracy, and it wouldn't take a K-F scientist to figure out that the IS Houses are too busy trying to kill each other to pay attention to the Periphery...which makes the TDF's priority killing pirate forces that are likely built on the remains of defeated/smashed House or merc mech units, all of whom are likely to be no more than company-strength, rather than organized invasion forces. That's going to hold true up to 3025, easily.
3. Which brings us to 2800 and SC. If the Houses aren't smashing each other flat, were I sitting on the TDF General Staff my main focus would be on the Suns and the CC. I'd want to organize and build my forces as rapidly as I could to make "adventures" against me extraordinarily bad ideas, and I would want those forces configured for combat against a military (vs pirate) force...which indicates that they would need a more conventional organization, to maximize their forces deployment.....
...However.
This now brings us into the realm of mech and Jumpship/Dropship production for the TC, and the question of "Do the Taurians have one or more of Amaris' secret mech plants under their control, and if so, what is its output per annum?"
As well, did the TC have its own shipyards PRE-Coup? And, in the absence of SW 1 & 2, would those facilities survive?
In the absence of C* killing off scientists during SW2 -
- I simply cannot see the Taurians not utilizing their education system to start building remote yards and mech plants, whether they have Amaris' sites or not......