I think the solar electricity thing is about the minimum charge rate the car will accept, this isn’t unusual in EVs and you’d set it to charge at the minumum rate & draw a mixture of solar and grid electric to achieve that level.
The rust issue may have been down to there being no wheel arch linings, so when you open the bonnet you can see the inside of the wheels. This is something you’d see in cars from the 1960s, which rusted, but with the really thin panels of modern cars they would rust through without those plastic wheel arch linings in months, the MG ZS EV proves this.
Now you can buy wheel arch liners for the MG ZS EV you can fit them yourself & potentially solve the problem for a while as long as you know to fit them before the car is driven with salt on the roads.
There are reasons the MG ZS EV is comparably cheap, it’s missing features we’ve all got used to in cars. It’s still a good basic EV though.