Ergon grips are awesome. I ordered my Tikit with them installed and I love them. I commute about 40 miles a day and I switch back and borth between my "normal" fixed gear bike with Nitto bullhorns and my fixed gear Tikit with Ergons and when I ride the Tikits my hands and wrists thank me. For ~$40 this is one of the best upgrades one could make to a stock Tikit.

The rear rack definitely makes the bike more stable when folded. I have never had an issue with the bike tipping over whereas when I test folded a Tikit without the rack it seemed more difficult to get it to balance. For $50 this is a worthy upgrade.

I have the stock mountain bike handlebars with a 5 degree bend that Bike Friday defaults to on most built-to-order Tikits. These are great when paired with Ergon grips. I feel I have still have the ability to ride fast if I want but this setup also encourages me to relax and enjoy the view more often than on any other of my bikes.

Replacing the rear triangle? Are you nuts? :-) By the time you do that and purchase an internal gear drivetrain I would think it would be easier to sell your Tikit and just let Bike Friday build you a new one or wait for a used one to pop up on their site. But it does sound like fun.