Has anyone had any experience putting an aftermarket, field-installed tile flange on a Victoria + Albert limestone resin tub?

Our situation is that back in 2008, we ignorantly had an old, cast iron, alcove tub put in, that does not have a flange on it, to be used as a tub/shower combo. The contractor told us that the tile setter would seal it so that it wouldn't be a problem. Unsurprisingly, now that I've learned more, it turns out that it was a problem and we ended up with significant water damage behind the wall and into our bedroom on the other side. We didn't have the resources at the time to redo the whole tub/shower, so we fixed the water damage as best we could from the other side and just put up a second shower curtain against the wall to keep water off it. Then, a couple of months ago, we had another leak from corroded plumbing, which led to more water damage, so we're finally looking at pulling out the whole thing to repair the damage and finally replace the tub with one that has a flange.

I thought I wanted another cast iron tub, but I just got introduced to the Victoria + Albert limestone tubs, and I really like them. But they only have one alcove option with an integral flange, the Kaldera 2, and it's 60x32, whereas our space is 60x30. They do have a 60x30 Kaldera 1, and the costumer service person at Victoria + Albert told me it's not available with an integral flange, but that I could buy an aftermarket flange to put on it. She did not have any recommendation for what kind of aftermarket flange.

I'm a little nervous about more water damage at this point and really don't want to put something else in that's going to end up being a problem again. Do any of you know if putting an aftermarket flange on the Kaldera 1 would really be a viable solution? And if so, what kind of flange we should look at?

OR, could we just put an aftermarket tile flange on our existing cast iron tub? Would that be waterproof?

Thank you!