I’ve got a number of the CSXXA series speakers- beautiful enclosures, but honestly fairly sub-par drivers. I am definitely not one to “upgrade” (so to speak) drivers in the enclosures with non-originals. I always stick to the originals. That being said, the tweeters in your 88’s are really not much of anything sonically. If you really want “to get them going”, you might want to consider temporarily swapping them out with aftermarket speakers - you may like the improvement (while patiently waiting for the originals to come along on the auction site). I would expect that you could find some reasonably priced alternatives that would fit into the existing ports. They won’t be brown like the rest of the FB drivers, but may be an overall sonic improvement.
This all obviously depends on your goals, timeline patience, and financial parameters. Just an idea... Parts Express usually has some nice options at decent prices, and usually has close-outs that may fit your need and budget as well. You’ll also have to consider how to equalize them with the other originals. Good luck to you!