Late to the Technology game, and struggling...

I would never try to sight read a song I've never played before. That's a disaster waiting to happen.

Most of the time, I'll learn the songs in my basement, but not playing the same songs every gig may have me go a few weeks of not playing it. And then I can freeze up because I can't remember all the parts.

I've used tabs before to help remind me of patterns or portions of songs, or even to trigger my memory to get me started.

I'm thinking having these notes in a tablet versus a huge paper binder would at least look better.

As far as him using capos out of the blue, it's just a matter of shifting your fingerings fpr a given song up the same amount of frets that he places his capo. Unless you're a bassist who plays a lot of bar chords (most don't) you'll likely never need a capo.

It can still be a pain in the ass having to adjust though, especially if you're used to playing a song in a certain key. Muscle memory's great but it can be a bitch in this kind of situation, as you could be in the middle of playing a song and your fret hand reflexively drops back down to where you're used to playing it, and suddenly you've lost track of where you're supposed to be. Happens to the best of us. Which is why it would still behoove you to tell the guy, hey, I need to know when you plan on busting out a capo, so you can familiarize yourself with the new fingerings beforehand.

As for technology what about a laptop with Guitar Pro with all the songs loaded up, just open the file and run it when you need to and play along.
This has highlighted a sad fact, there are bass players and then there are people who play other people's basslines, I fall into the latter. My youngest brother is the former. I got him into bass but he took it to the max, he mastered one of Jaco's most difficult lines to pass the entry exam to get him into college, he site reads and gets regular session work because he walks into any situation and just plays whatever is required, and is looked up to by his peers rather than down on cos he didn't learn U2s With or Without You from start to finish, his warm up excercises make me stay away from the bass for months on end

Our band collectively decide our song list for rehearsals , I'm generally the one who chooses what we will play from that list in a set only because somebody has to do it

We put a prompt next to each song so we remember how starts it ,drums,guitars,bass or vocals and that's it - songs should be learnt by that point

Our biggest problem is laying off the grog, but its the one thing we always forget