I personally think your gauges are backwards.
You mention you will have a boost Controller. Does that not tell you your boost pressure? Are you worried about it not controlling the boost correctly? I have always thought the boost gauge was a bit useless (I much prefer to have my eyes on the road when my car is boosting hard).
A/F gauge. Why do you need this? I see them more as a tuning aid then anything else. If you have EFI tuned properly, I don't see why you would need this for anything other then during the tuning phase, which would mean you could have it temporarily mounted.
I personally think Water temp and Oil pressure are a must, would like to have oil temp as well (Had a car drop its water and I had no indication as the water temp gauge was no longer sitting in water and was therefore reading normal, not a Z). I guess Oil pressure could be replaced with a warning light.
Personally, I think I could lose fuel gauge (Especially since mine doesn't work at the moment anyway), but would prefer not to.
I find voltage handy, as I like to know that my alternator/regulator is doing what it is meant to, but I think it could be replaced with a warning light for low or high voltage.