The whole problem with this is putting enough cars of similar spec together for the day,and then dealing with the disappointments after!
I think it would be fun to do it,but you'd need to ensure a level ground first,in terms of boost,fuelling and hardware,which is easy enough up to Stg2+,but really hard after that due to the differences in hardware between tuners,even with the same software mapping(and even that's mostly been customised for individual cars).
If I was going to go properly for some big mods I would use your build thread as a shopping list and go Revo. Anything else would be pointless!
We should do a mass RR day for fun, given correct time/location I am up for it. Almost impossible to do a comparison which is objective. For example I rarely agree with EVO magazine group tests as I don't like 911s. Purely subjective based on shape etc.