Hi potatosack.
There is nothing wrong with the concept of a table top game that plays more like
DoW does.
As it would be loads of fun I am sure.
Its just the current rules for
40k would not be a good starting point.(Alternating game phase.)
Mantic are releasing a new rule set for Warpath this week end.This might be a better starting point for the sort of game you want.(Alessio Cavatore is writing these new rules so they should be ok!)
Have a look,(they are free to download beta.)See what you think...(Alternating unit activation.)