That's not supported(*), but you can probably come up with something that works...
If you create a new virtual drive in PoL (Configure button > New button (bottom left) > 32bit, System, name it say PlainWine), and then have a look at it in ~/.PlayOnLinux/wineprefix/PlainWine, you may notice that it looks a lot like ~/.wine, with a few extra files, probably playonlinux.cfg and playonlinux.log.
At that point you have multiple choices, copying or moving Wine files over the files of PoL virtual drive, or symlinking ~/.PlayOnLinux/wineprefix/PlainWine to ~/.wine; Just make sure you preserve the extra files that PoL needs.
Once that's done you can manually create shortcuts to the programs you want to start from PoL interface: Configure button > (select virtual drive) > General tab > "Create a new shortcuts from this virtual harddrive" button)
- if it breaks you can keep the pieces.
- the behavior of PoL with state it didn't setup itself may change in the future.
Edited by petch