I'd suggest making a guide slot that resembles a sawtooth pattern, where the shift handle has to deflect sideways a little to change positions. It's easy to fabricate from a piece of aluminum or stainless steel. If you really want to get creative, get out the stamping dies and label the positions. The old Chevy cast iron Powerglide had Reverse at the bottom of the quadrant, and no reverse lockout. (P-N-D-L-R) I've grabbed "R" a few times in a 55 passenger car when trying for "L"! That's a real attention-getter!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!