Nope. Still confused.
If you want to make bridles, go ahead. You don't need sleeving on bridle lines.
You're talking about making line sets for your three kites? 4 lines x 3 kites x 2 ends per line = 28 sleeves. How would getting the loops off broken kite lines help you? Are you going to tie them onto the ends of your lines? Really?
If you want sleeving, do as I said earlier. Buy some 2 or 3mm sheathed line in two colours (red and black or blue or whatever). Pull the sheathing off and use that as sleeving. I used to cut it to length then put a nail in the end then melt the ends to get a neat end and stop it fraying. Don't melt it too much or you'll get a thick, hard end that will catch in the sewing machine.
It's easy to sleeve line. A guitar string will do to pull stuff through. A D-splicer is better. Even more useful is the D 16 scissors for cutting Dyneema.
d-splicer.com/You can sleeve spliced line and that's still easier and stronger than sewing loops.
For making bridles I used to use a length of timber as a measuring jig. Hammer a nail into one end. Make your first loop. Hook it over the nail and your steel tape also over the nail. Apply tension. Measure. Mark. Check a few times. Cut, sew, trim. Check again.