Couldn't resist jumping in on this one. I do this all the time with my system modules.
Best way I've found is to create one more line item formatted as a number, similar to your comment line item, and 1 if TRUE else 0. Set your conditional to be the most likely so if there are more unchecked then checked then write the formula as If false then 0 else 1. You always want Anaplan to exit the conditional as fast as possible and it looks like you're using a lot of dimensions so this will be important.
The last part is to write the SUM which will just be reference (without the SUM function) if you're using a structured list. If not you'll need to use the SUM and/or TIMESUM function.
Very well done and absolutely correct. One suggestion on the module without the time list, try to avoid using TimeSum as it is a single threaded calculation. As an alternative, in the Time settings, click on Total of All Periods and do a Select at this level (Checkbox Sum.Count[SELECT: TIME.All Periods]) , again if the target is not using Time.
If your source module is not using Time but all lists have a Top Level, then the Select will not be needed.