Access to IIgs features from BASIC with 65816 glue?

[Lyrical Nanoha <LyricalNanoha@dosius.net>]

I've got a real bizarre idea I want to experiment with...

I'm fairly familiar with the 6502 and quite familiar with the older Apples 
but never was able to make use of the IIgs's additional features...

I wonder, how hard it would be, to come up with a program to interface 
between BASIC (using & commands) and the IIgs's 320x200 and 640x200 modes.

I am thinking of doing some graphical stuff on the GS and only way I can 
really interface to the computer at all is BASIC or very simple ASM. :(

-uso.