This is a helpful idea. I like this, and would wish for more calendaring / group scheduling features along with this. (Such as being able to post a calendar icon showing various game-days upcoming, even if it's not weekly or monthly but perhaps it's Tuesday this week, Thursday next week, and Monday + Friday on the 3rd week). For now the GM can easily make an RSVP Thread in the campaign's forum to serve this function. This is what my DM does, and when I'm running a game I do this. The functionality is similar to what you're asking, if less elegant. Make the thread "Who is playing in our game on this Friday Dec 19? RSVP here" and Players are expected to respond, Yes or No. Alternately you can make a Scheduling thread for "Regrets only". Then players are assumed to be a "Yes" unless they post in the thread saying they won't be able to make it. Here is a Related but not identical Suggestion that came up, you may want to look and consider comment / vote /support for this one too, <a href="https://app.roll20.net/forum/post/1629718/calendar" rel="nofollow">https://app.roll20.net/forum/post/1629718/calendar</a>...
