Can this shower stall be saved?

I have a house that was built in the early 1950s. It still has its original shower stall on the first floor, with the standard seafoam green tiles. The shower was built with its floor tiles set into a concrete slab on a lead pan.

Over the last few years the lead has deteriorated (and the concrete has cracked) to the point where water comes into the basement in torrents whenever we try to use the shower. We brought in a contractor who said that it would be too expensive to fix the shower, and instead suggested we convert the tub to a tub/shower. However, that presents its own set of problems; since the tiles around the tub don’t go all the way up, we’d have it finish it off with mismatched tiles (we couldn’t use the ones from the shower because they’re not the same).

Anyway, it seems to me that we could just remove the bottom row of wall tiles, break up the concrete, install a new pan and then a new shower floor. Is that realistic? Or is a new tile shower floor like this really expensive?