Both are viable options, with their own pros and cons. I've seen more MGs do TDMs over Mock Weeks for that very reason, I believe. Since with a TDM, you're free to hop in whenever whereas reserving for a Mock Week can be over and done with quickly before anyone has the chance to open the page. A medium between the two could work? Could you explain what you mean by scheduled updates to the TDM? I'm a little lost.

And I get that! Powers in MGs definitely helps spruce things up for events such as case planning, where someone's power may come into play during the case. The game I was in had powers mitigated and nerfed, to where people could still use certain powers, but less powerful than they are in canon.