Just to let you know there is no such thing as a VCA output. They don't exist on any console because vca's are not used to subgroup in the true sense of the word they control subgroups or what ever is assigned to them but they work on a dc voltage of 0 to 10volts then they re rough the audio back to the input or output in question. I don't use subgroups on a console I prefer like most sound engineers to assign everything to left and right. The only time I will use subgroups is on small shows where there is not enough compressors for vocals. But more often then not I will use the VCA'S if its a good console like a pm4000 or a XL4 or Heritage 3000. But never on a cheap console. And as for asking me for a discrete mix. That's not likely going to happen as a front of house engineer all of your time is spent getting the mix together.
I'm not suggesting taking a physical output from a VCA, since, like you said, there is no such thing. What I was suggesting was routing your VCA's to the matrix section and setting up a recording from there. As for subgroups, I tend to use them on big consoles, but on smaller boards, I'll just route everything to L&R. It doesn't matter if you use subgroups or not.....the signal eventually gets to the L&R outs no matter how you decide to route it. If you do use the subgroups and set them up with, say, drums in 1&2, horns/toys in 3&4, bass/guitar in 5&6, and vocals in 7&8, then you can route the subgroups to the matrix section. Fader moves on the subgroups will affect the tape feed, but fader moves on the L&R main outs won't. That was my point.
Also when you get a matrix out from the console if there is a eq inserted on the left and right you might get that going to tape because on some consoles the effects send and matrix input are POST FADER from left and right Not pre fader.
Matrix INPUTS? Never heard of such a thing on a console. Matrix inserts, maybe, but matrix INPUTS? Not that I am telling you anything that you don't know, but a matrix is simply a way to route a signal to various outputs....such as a record feed, a press feed, a delay feed, etc..
And as far as EQ inserted on the L&R, that EQ will NOT affect your recording if you set up a matrix of your subgroups, since the signal never hits the L&R before it gets to your feed.
I fully understand what Phil is trying to accomplish....but there are many ways to get there...not just the main outs. You just need to know what to ask for. Oh, and as far as the engineer being too busy to set that up for you, I say that's weak sauce. It takes about 10 seconds to turn up the knobs to make this happen. I do it day in and day out for corporate events when the client, at the last minute, says..."this guy is with out Multimedia Department and needs an output for his video camera". It takes longer to walk to the backside of the console to physically plug in his cables than it does to dial in the matrix mix for his send.
I'm not trying to argue here...I'm just saying there are many ways to accomplish a decent recording of the board, and, while asking for the main outs might be the easiest, it's not necessarily the best.