Basically I'm using the Brotherhood of Shadow approach where the solution is just loads of explosions and fade to black mid-way through the explosions, just like Hollywood would want. Then when the fade to black is done, the new module loads, you're at the same spot you detonated the charges. Now we have a newly blocked cave and a new tomb that was now "exposed" offscreen, i.e the TSL cave module instead of the Kotor 1 module.
I don't think it needs to be that complicated, Kotor was never really creative about stuff like this in the first place, TBH.
You could have the Sith students tell you there's a hidden tomb with all types of artifacts and goodies and stuff hidden near the cave exit. They could provide you additional explosives to blow up that area directly as well along with the cave exit. This would be a nice reference to the Thorium charges from TSLs Korriban. You would need to plant explosives at both the cave exit and the area where the tomb would be in TSL, then detonate both at once (and not only one at a time due to obvious reasons). Why both at the same time? lol idk make up a story reason in-game. The actually reason is because there's no module with only one change, it has to be the two new ones (no cave exit, new tomb area)
The idea might not be the best, but it's simple and I think it could work.