Processing should be capable of boosting the blacks.
I’ve tried to explain what is going on in this area several times but often to no avail. These are the gradation curves built into an E-M1
Each of those curves represents a camera profile. Bottom axis is raw stops in, vertical jpg bit depth out. The slope of the line indicates contrast. It always tends to get lower at each end of the brightness range. When a raw file is opened in an editor what is shown is the jpg bit depth after some curve of some sort is applied. The idea of PP is to do what ever you want to do with it and that can include in a simplistic fashion all of the stops in the raw file but the fact that this is more than can be shown on the screen means that contrast in various places on the tone curve need to be changed. That is what things like highlight and shadow recovery actually do.
Can’t understand how you can get posterisation other than having the wrong working profile or working adobe rgb in srgb or simply pushing things a lot further than they can be. aRGB even with the correct equipment is more likely to have that problem sooner.
Personally I feel that you should be ok with any of the adobe profiles other than maybe high key if there is one and it’s better to try and get to grips with pp rather than trying to achieve what you want to do via profiles. The important thing is a camera auto white balance that works reasonably well in most situations. The colour scaling factors used will have an effect on that so in some respects it’s best to dig out the ones that are provided in the manufacturers software but adobe should achieve the same thing. Faithful,natural or neutral may be a good starting point if there are any named like that or standard.
John