A 'backup knife' is something I've considered. I've skipped on it here because of a lack of space, and I find that using a knife for gear repair can be dangerous...and I have plenty of backup knives already (I carry 2 to 4 already not counting kit backups).

I would consider adding a small SAK though...something with an awl and scissors would be ideal. I pretty much exclusively use my Victorinox Cybertool for gear repair tasks.

The alcohol pads are for surface prep before using any glue or seam sealer...make sure I only have to repair something once.

UPDATE: I just came across some single use (0.5mL per tube) Krazy Glue in a kitchen drawer and I've added 2 tubes to the kit.