if it's workable, i'd love to have the option of forcing the client to finish to work unit it's on currently, instead of switching at some random amount of time. unless of course this is already implemented and i just couldn't find the option.

simply set the time to switch between applications higher than the longest WU's you are running. unless boinc get's into panic-mode because you have too much work in queue, this will do the job.

You could achieve this behaviour by selecting from the Advanced tab -> Preferences -> Processor usage

There you find other options: Select between applications every ... minutes (default = 60)
If your work finish e.g. normally within 12 hours, fill in a bit more like e.g. 800.