Apart from it being a lot harder to schedule a game when four specific people need to be there rather than just two, do people/you actually prefer external commentary?
I definitely prefer just having one of the players talking, and I quite enjoy commenting on my own games, I'd only be willing to give that up if I really cared about the match (b.c. commenting makes me play a bit worse), which may or may not be the case with some kind of final or challenger/defender match, but definitely not with regular A league games.
The schedule difficulty is the same for any match, making it champion/challenger won't change that.
It takes the same number of steps but people will be far less willing to actually take them when the event is less special and prestigious. It's the same reason why people are willing to pay a lot more to attend the world cup final than they'd pay for a friendly between the same two teams.
To make the Gokodom final commentary happen, Mic had to buy a mic (heh), I had to discuss with Andrew how to best set things up, Andrew had to test various configurations and streamline it with us and Jog, then I had to reschedule some stuff I had already planned and leave a visit early when I heard about some train nonsense that resulted in significant delays. Would we have gone through the same effort had it been a regular A league match? I can't speak for the others but for me the answer is "hell no lol".
You might want to argue that without a champion/challenger, the A league games gain in prestige, which is sort of true but with there being 15 of them and few if any of them being deciding on their own, they're just going to be less special no matter what, and while I'd be willing to comment if it suits my schedule, I'm certainly not going to go out of my way to make it happen.
Additionally, I'm very reluctant (maybe even flat out unwilling) to let others comment on my regular league games because I too much enjoy doing so myself, whereas I might be open to it for a potential champion/challenger match.