You make a good case for consideration. The devil is in the details here.
Concerns include:
1. San Diego location. Not the best location to attract lots, although Feb timing is mitigating.
2. Because MAS/Sage never created one, the inertia in the customer base is to Partner-based UG. I don't see the large partners giving that up willingly, so why would they participate (spend money) in 90 Minds? I don't know, there might be legitimate forces moving them out.
3. There are essentially 3 relevant customer segments.
a. Customers who intend to migrate out from Sage. Low interest in 90MUG
b. Customers who will stay with Sage,
(1) but have little budget. They keep doing what they've been doing. I can't see them joining, but maybe.
(2) and who see how it can meet what they need for foreseeable future. They likely have good partners.
What is their benefit from a UG?
4. I don't think this works well mixing with MOTM itself. However, I can readily see it as a 2-day event immediately following.