Re: Problem of Bulk-driven
Yes you can, as long as the CMOS process is P-Substrate based with N-Well. All you need to do is create separate wells for each of your PMOS devices (keeping in mind all DRC rules).
There are a couple of disadvantages though. First one is that the area of your design is going to be much larger because the distance between the wells of your devices usually needs to be large. Second, is that if you want to design, for example, a bulk driven differential stage, you won't be able to use any techniques to minimize mismatch (like for example inter-digitated fingering) since your devices need to be isolated from each other.
Hope this helps,
diemilio