In version 14, up to 200 report suites could be added to a single rollup. In version 15 rollups were overlooked in the initial release, but eventually were included. The cap, however, dropped down to 40, which is well under the size of many of our rollups.
So if you can't increase the number of rollups allowed, you should be able to nest them. Client Care told me it would cause problems if the nightly roll-up function was occurring on the nested account before the individual rollups were done, but you could kick off the process for nested rollups the following night. Obviously, there are many ways you could fix that issue and give us more flexibility in our roll-up reports.