Possible to make the taskbar function like this with only a theme?

So I've just begin to get into creating custom themes and I am definitely waking into new territory here. I have the Start Orb customized; however, after some research I think I've hit a limitation with the taskbar and will not be able to follow through on my plans. I'm needing to know if it's possible to customize the taskbar like in the image below (I quickly toss it together in photoshop.). I'm not afraid to dive into executables and DLLs if I have to in order for this to work.

Before:


After:


From what I've read, this is not possible to just with just themes (changing images). Just seeking confirmation so I can stop researching and revise my design for a full taskbar.

EDIT:
Also, if someone could point me to a guide that has all the image numbers and what they correspond to for the styles that would be extremely helpful! I've searched a lot and most aren't accurate (I'm using the default Aero theme as a base and Restorator). The closes thing I've found is this: msstyle.info - Edit and modify aero.msstyles image numbers and it doesn't have everything. TIA

Thank you for your reply. Looks like I'll be rethinking my design a bit.

Also, thank you for that link! The reference images will be most helpful!