In the vast majority of cases particularly with the kind of covers we have available in the Australian market, a pool cover will almost always need to be attached to a pool cover roller for ease of handling in both putting on and taking off the cover, unless of course, it is quite small in size.
So therefore the question of whether fitting a cover to any shaped pool is possible does not rest with the cover itself but whether or not a roller can be installed and whether the shape will lend itself to being rolled up with relative ease.
Cutting a plastic pool cover in on any shaped pool is possible for an experienced installer, but a roller is a fixed size and shape and needs to be able to stand in the correct position on the pool deck relative to the pool in order that the cover roll up process can be performed with relative ease.
Where we run into some difficulty mostly is in tight pool enclosures with very little free access room around the pool. This is a big limitation on where to set up a pool cover roller.
Jagged rock gardens that run right up to the pool edge can be another difficult area even if you can get a roller in because I force the cover to be pulled over those jagged rocks in order to put the cover on and take it off, with the high risk of damaging the cover each time.