I would like to bring up the idea of playing with an extra infielder. This would reduce the number of players trying to hit up the middle when the homeruns have been exhauted and thus protecting the pitcher. Has this ever been discussed?

Yes, it's made the rounds, do a search and I think you'll find both sides to it.

We used to run a 5-man infield in the 35s and 40s just to make the opposition have to think. It sure changed some of our games for the better (for us)! Of course, you need 3 gazelles in the OF!

I am a big fan of the "5 man"
If you have three OF that can cover the ground a 5th infielder can be a big advantage providing he knows how to properly play that position. The 5th infielder is really effective if you are playing with a mushy ball.:)
Yes, players are less likely to hit the middle if you have the above in place.

In the SPA Winternational this past Oct, the Pensacola Merchants played a 5 man against most competition. I was trying to place the ball between the pitcher and middle infielder when I missed the hole just a little. I appologized the the pitcher after hitting his shin with a one hopper. I didn't get the pitch that I had hoped for.
So, the 5 man wasn't a deterrent for me, maybe I should have thought twice about it. I'll remember his shin for quite a while.