You make a good point, I'll discuss it with the developer.
I do know that it's very difficult to get BOINC and FAH to find a suitable balance. If you want to split your time equally, I recommend a week on one and then a week on the other ... (ending FAH with the FINISH function)
Alas, I'm a set and forget type of guy. I run a small data center and really don't want to have weekly tasks to do. I only allow FAH CPU work on my larger servers (32+ cores), since I figure those are somewhat rarer than the typical home desktop I5/I7/Ryzan based systems. That said, I've noticed 32 core work is hit and miss, so would like BOINC to run in the background to soak up anything not used by FAH.
v="nice=n" and allow the owner to specify the n. For instance, I have storage servers that use next to no CPU power that have been repurposed into that role. They have CPUs to burn currently, so nice=0 make perfect sense to me, or perhaps nice=4. Given that Unix nice values are not absolute priorities (eg, even nice 19 processes get some cycles), having cpu hogs at nice=0 will not render the machines inoperable.