Well i must say I am not sure how exactly to solve your problem, but it seems you would just like to be as lazy as possible as typing an 's' to get the
file you want is hard work.
Let me put it to you a different way, what do you expect the default action to be if you wish to tab-complete a command?
With your method, instead of being presented the alternatives and simply choosing the next letter to get what you want you would have to
keep tabbing through all the alternatives. Here is an example:
If you perform this action on my linux box I am asked:
Display all 133 possibilities? (y or n)
Your solution would have me tab through all 133 until i see the one i need/want.
Maybe you should consider what happens here before trying to alter the current scenario.