Shout-out to karencon
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I don't know anything about the feasibility of building up the curb over it, but I am guessing it would be possible if done properly.
The lip of the pan gives you 2 1/2" in depth so I think a shower curtain would remain inside. However, the shower itself is not a large one. Because of size of the shower stall, there might be a greater impact of water spray hitting/running off the liner than in a larger space. If the person(s) using the shower is careful to make sure the liner is tucked inside the pan before, and during showers, you should be ok, Also, he/she would also need to make sure the hem of the liner remains inside the pan after showering, or it will drip all over the floor outside the shower. I sometimes have to remind myself to make sure the liner isn't hanging outside the bathtub after I take a shower in the MB, or I end up with a puddle on the floor.
FWIW, same thing with the glass shower door--when we used that bathroom, we tried to remember to close the glass door after stepping out of the shower, in order to avoid mopping up a puddle from water dripping off the wet glass.