This option #3 makes me wonder if a back lock could be moved even closer to the pivot to deliberately benefit index finger operation. Maybe that plus a lighter spring could make it a much easier lock to operate with a weaker finger. A weaker spring doesn't have to mean a weaker lock, consider how soft the Omega Spring is in an Axis lock...granted these are completely different types of locks and springs but I think with some tweaking you could make a back lock just as reliable but with a much softer spring.
But like everything else, is this a solution looking for a problem? My first Spyderco was the original Native and I thought it was genius how the choil fell onto your finger when closing. Back locks are one lock type that I think should always be paired with a 50/50 choil for this reason, especially since otherwise the kick is just wasted space anyway, it may as well be shaped into a choil if it has to be there.
SHARPEN IT LIKE YOU LOVE IT, USE IT LIKE YOU HATE IT