I am currently building a racing panel for my homemade cab, and have run into the same issues.
For gear shifting w/ a pole position shifter, I think I may have another option using my Hagstrom ke72 encoder.
The ke72 can be programmed so that a keystroke is generated when an input is released. I plan on configuring it to send the same keystroke when the shifter switch is pressed and released. The only problem, like DO!'s dual switch solution, is that the shifter will need to be in the 'LO' position before the game starts. If this gets annoying, I'll probably do the recompile thing.
As far as pedals are concerned, I'll will be using a Super Offroad pedal, and a Happ "flat pedal" (part no. 50-8195-01). They both have potentiometers, but I will be retrofitting them with actuator plates and "roller" microswitches I ordered from Happ. Since the pedals already have mounting holes for the switch/actuator, I hopefully can get by w/o drilling or cutting. If I get ambitious, I may reinstall the pots and try the dual strike hack later.
Also, I will probably have one pedal "slideable", so I can have the pedals close together for a gas/brake combo on single player games, and farther apart for multi player games like Super Sprint and Super Offroad (my panel has 2 wheels, btw).