Just because I have no idea how f-droid works, why is that? I have a hard time figuring out the rationale behind this choice.
Also IMHO apps building, in addition to fifo, should take into account some kind of priority e.g. (top to bottom): security upgrade, broken app upgrade, standard/new features upgrade. Every time an app is built, the builder should check what the next high priority app is in queue and needs to be built, if any. Just an opinion of an outsider, I don’t know if it’s feasible right now.