Chris,
I've come up with a way that is similar to yours but instead of six sided dice I use 2 ten sided dice (each a different color) with one regular six sided dice. So when I roll the dice I roll all 3 at once. Here is how it works. I have 10 running plays, 10 passing plays, and 10 defensive formations. I roll the dice. The single 6 sided dice is the key. If it is an odd number it is a pass play. An even number means a run play. So if the offensive dice is a 4, the defensive dice a 2 and the regular dice a 5 then the play is for the 4th offensive pass play on my list. The defense sets up the 2nd defensive formation on my list. If it is an obvious run OR pass down (i.e. 4th and 1 or 3rd and 16 as Scott pointed out earlier) then I don't use the 6 sided dice. I just use only the pass or run play list. This allows for more plays than what was presented earlier with just the six sided dice with only 6 plays. You can get the 10 sided dice on the internet for less than a buck each. I got mine at Trollandtoad.com
http://www.trollandtoad.com/Supplies...1204p1n10.html. You can also get them with more than 10 sides (20, 30, 40, etc.) if you want more plays.
Still trying to fine tune it but it's fun so far. Will resume playing with it after I finish moving next week.
Your thoughts?