I have the clicker type with a manual in my Bronco. I really like that. I've never used one that would automatically return to idle, so I can't say for sure, but I really don't think I'd like that as well as the clicker. I use mine to step up the idle when the engine is cold (manual choke with no fast idle cam).
When I need a foot on the brake while letting out the clutch I set the idle higher before letting out the clutch. I can use it like a more typical hand throttle, but there's really no need to. Just setting the idle higher works well, without needing to feather the throttle. And there's really no safety issue with having it not automatically return to closed throttle. It's only idling at about 1500 rpm usually, so it's not like it's going to speed off once the clutch is engaged.
I do the same thing with rock crawling, especially when crawling up a hill, setting the idle up a click or two to keep the engine from stalling. Of course the 4.3:1 Atlas helps keep the speed low enough that I can do that without beating everything up too bad.
As far as conflicting linkages possibly binding, I don't see that being a concern. If you look at the pic of the connections to my carb (above) you can see a pretty long cable run from a bracket on the firewall to the throttle. That's the hand throttle. The foot throttle of course is the solid bar below that. When you open the throttle with the hand throttle the stock linkage pushes the gas pedal down. And when you open it with the foot feed it puts some slack in the hand throttle cable, but there's nothing for it to get hooked on, so that's no big deal.
