He never brought up the topic with me, though I only dealt with him personally in 2013. Back then, he still "publicly" or "officially" got along with Bishop Williamson.
Even if he never brought it up explicitly with anyone, or produced "Joseph Pfeiffer for Bishop" signs to place in one's front yard, it doesn't mean he doesn't want to be a bishop. There are other ways of expressing this desire.
Actions speak louder than words.
Publicly opposing the only Resistance bishop? Check.
Publicly criticizing the only Resistance bishop? Check.
Starting, running a seminary? Check.
Happily taking (or trying to take) a nationwide/global leadership and administrative role, even as a priest? Check.
Inviting a dubious con-man "bishop" Ambrose to work with your group? Check.
Ignoring countless red flags about this con-man "bishop" Ambrose? Check.
In many cases, stubbornly going one's own way, even in opposition to the guidance of the Resistance bishop? Check.
Already acting the part? Check.
Any motivational book will tell you: if you want to be promoted, start acting the part now. SEE yourself as a manager. Act like a manager. Take on extra duties and show that you could manage the operation. Show initiative. Eventually, you'll get promoted to that position. Meanwhile, these books will point out that you can't say, "Trust me, give me a chance, and I'll show you what a good job I'll do! Give me a raise, and I'll work much harder!" No, you have to work much harder and THEN you get the raise. That's how the world works.
See, even if Fr. Pfeiffer said with apparent sincerity, "I would never want to be a bishop." I would have a hard time believing it; it would be shocking to hear, since everything he's doing in his life goes against this. If he expressed sentiments of humility or unworthiness, it would also be HUGELY out of character to his usual modus operandi of "I know best".
Yes, I'm criticizing Fr. Pfeiffer here. But come on, this is very clear-cut. I'm not nitpicking. Just look at Pablogate! He won't dis-involve a known apostate like Pablo who has certainly done A, B and C and probably X, Y, and Z as well. On the contrary, he stubbornly keeps him as his right-hand man. What, is he waiting for him to become the next St. Augustine? Father seemed a bit overboard in his sermon about St. Augustine "The greatest bishop to ever walk on the ground." I didn't think that was the common opinion -- surely there were other bishops at least equal to St. Augustine. What about St. Athanasius? or St. Pius X?
So, to summarize, I've never heard Fr. Pfeiffer express an explicit interest in becoming a bishop. But he has shown a desire for power, leadership, prominence/fame, a refusal to follow the existing 2 Resistance bishops, and he has a seminary (which he started completely on his own volition) that needs a bishop to ordain and confer minor orders.
Simple priests -- who want to stay simple priests -- don't start and found seminaries. Archbishop Lefebvre started several...but he was a Bishop, not a simple priest. Normally Church authorities take care of the business of forming new priests, or at least (in a Crisis situation) a bishop -- he has a certain responsibility just by virtue of his office.