I've done the same as you when I book a large block of rooms. I also find the central Marriott Group Sales group to be a pain to work with. So I normally bypass them completely and call the hotel directly.

Unfortunately, as far a Marriott Corp is concerned, you will only get the points for up to 3 rooms. With that said, normally when I set up the rooms with the hotel, I talk with the GM. The last 2 times I have done this, the GM gave me some bonus points to help out. I think the last time, which was this past January at an RI in Arlington, TX, I was given something like 10K points as a bonus. It didn't replace all the points I would have received if I went through the Meeting group, but it was a nice gesture. So I would suggest you talk to the GM and see what s/he can do for you.

Another thing that I usually do is when I check in, I will give the front desk person the MR# of my wife and some other friends who are staying there. That way, they will also get points for 3 rooms. So far, I've never had any issues with my paying for the rooms, but them getting points as well.