Well, I'm certainly not a professional when it comes to the use of BEMCLI, but if I understand it correctly, it's possible to execute BEMCLI commands via pre/post-commands and the windows scheduler. Given that BEMCLI can create new backup jobs, and, I would assume, delete backup jobs, it may be possible to do something like this:
Have your incremental job run from 7am to 7pm, only having it backup on its initial run.
Give that incremental job a pre command that will create an additional incremental stage that will run every hour, starting at 8am that day.
Use the windows scheduler to execute a BEMCLI code that will then delete the created incremental job at 7pm.
Now again, I'm not sure how viable of a solution this really is, as I don't really have very much experience at all with BEMCLI, but the thought just occured ot me and I figured I'd share it, in case it can be helpful. You'd likely need someone with a decent amount of knowledge of BEMCLI to do it, and it'd take some effort, but once you got it down, it seems like it'd be much easier this way than creating an army of stages for every job.
pkh talks about some of the functionality of BEMCLI here.
EDIT: Another option could also be to simply have it run the hours with the option checked to "Cancel the job if it is still running after <12> hours", though this would be a very haphazard way of doing the backup, which would throw an error of cancellation for the last backup every time, and could be potentially probelmatic. For the duplicates, you could have them run every hour with a cancellation after, say, 13 hours (or cut the incremental back 11 and do 12 for duplicate), having the duplicate start at 7:40pm (or however long it takes for you to be certain that the incremental will run successfully). Again, though, this method sounds like it could easily cause issues, but who knows, maybe it would work.
EDIT2: I'm also guessing that with enough knowledge of using commands, it would likely be possible to have a pre-command in an hourly incremental/duplicate that would stop the job after 12 hours in a more graceful manner.
