Most people would say that 64bit under 32bit on windows is impossible. However as far as I'm aware Wow64 works by loading a 64bit ntdll, then a 32bit ntdll. Calling the 64bit dll to issue syscalls. 
As shown in the Wow64SystemServiceCall, which is a jump to the _Wow64Transition.
Shouldn't it be theoretically possible to therefore load a 64bit dll, and do some sort of similar transition call between the two layers?
Just asking here if this would be theoretically possible, or if i'm wasting my time here. Thank you in advance!
Yes and no. You can't "load" a 64-bit library into a 32-bit process. But the operating system can run interference for you: it can load the library into another process, and supply an IPC interface to utilize it.
I worked on a project like that in 1995. Visual Basic in those days was 16-bit, and Windows NT 3.51 was 32-bit. We ported the computation engine from VAX VMS, a 32-bit operating system, and re-created the GUI with VB. To move data across, Windows provided a "thunking layer". VB called an OS function, passing a function name and parameter description. NT called the 32-bit function on VB's behalf, and returned the data in VB's address space. Worked like a charm.