I had a lot of problems with the maintenance reminders.
If they were to be added back in, I would prefer to see it as an email reminder to the tech (me).
This would be an absolutely useful feature too if you are providing service plans to customers that don't include labor based maintenance fees. Lets face it, when a system goes haywire and stops reporting with dSS, you simply don't know it right now. The only alternative at that point is to periodically contact your customers to see how they're doing, or to wait for their call.
How sound is the idea to have the email sent out by the client system? Not really in my opinion. It needs to be logged on the server, and then if the server detects that it breaches a previously set threshold "has not performed maintenance in 15 days", or "dSS has not reported in, within 24 hours", then it sends an alert to the tech.
This feature may not be possible with the current server setup. I think it would require a more advanced database and server side applications, sql, etc.