no one wants to really answer this question, because you all dont recommend the split boots in the first place,

There is a darn good reason, they do not work very well. But, if you are determined to use them, then go for it.

but would it be possible to just change the outer using a split boot without even pulling the rotor?

You have already heard the opinions on this, but the only way to find out is for you to try. It may look spacious, but it is cramped once you get your head, two hands and some tools in there.

And you do not have to pull the rotor. Please read what we've written. To do it correctly, you have to pull the spindle/knuckle assembly without disturbing the wheel bearings and/or the rotor/hub.

If you are going to sell it, just sell it. Don't waste your time or money on it. Leave the hubs the way they are. The next owner is not going to care either way. Knock off a couple hundred bucks off of the price and let them deal with the boot too.

Good Luck,
Michael