I have taken my ducky through a fair amount of class IV at this point, and thigh straps are a necessity. A foot bracing mechanism less so.
I ran my lynx with a Sotar inflatable seat as a foot rest for a while. It was very comfortable, but it developed a leak and I've been too lazy to repair it so I took it out and actually found the performance of the boat to be greatly increased. Having something in the bow that is not particularly hydrodynamic is a detriment to crashing holes - something that Duckies already do not excel at.
Right now I have nothing in the bow, and I can't say I miss it that much. Just ran a new section of class III+ to IV- last weekend (Little North Santiam River just below Opal Creek) and I didn't particularly miss the foot brace.
Is it better to have a foot brace? Yes, but I want to be able to roll my ducky up tight, and pegs tend to make this achievable. I will eventually make something custom out of foam with a drink holder in it (similar to above), but I'm not even considering pegs.
but can you see its opposition | comes a-rising up sometimes | that it's dreadful and position | comes blacking in my mind | ....and then I see a darkness