I'm not sure if the situation is that bad. And I THINK the drivers (also the stock ones) are derived from the SDK (but I could be wrong). However, if it is said that there are PowerVR SGX drivers which are less buggy than the ones in N9, it can be tried. Or, if the bugs are in open source parts, it can be fixed.

These are my observations till now:

1. I have not experienced such crashes in latest Nemo images. However, it might be due to not using as much graphics components/effects as SailfishOS.

2. There could be relatively easy fixes/workarounds for current problems, since they have some special nature: I can successfully run Sailfish voicecall-ui from command line always. But running it from GUI cause a crash almost always if 'voicecall-ui -prestart' is already running; and it tries to tell it to bring up the GUI, and it causes a crash in one of these locations (usually the latter):

A simple workaround for now (for all applications), is seems to be to disable all prestart and invoker single instance running logic with starting applications from scratch and closing them completely when not needed. This will make running apps slower, but you probably won't experience any UI crashes. I've not tried this approach for all apps, but at least it works for voicecall-ui.

As a side note, Qt libraries used in Nemo development images are newer than the ones in SailfishOS image, so I have a little hope that the new version comes with some bugfixes which could prevent such crashes. But it needs to be tested; it's just a hope!