The telescoping bottom bracket arm is more than sufficient to cover what a half-link would do. He is trying to get extra tension on the chain rather than simply trying to get a good fit.

Maybe, if you had a long bolt going through some bracket at the lip of the telescoping arm you could use it the same way as a jack but be lighter. If you did it right it could just stay in place.

I'm a little suspicious of putting a lot of tension on a really long chain though. Don't your chains wear out really quickly?