Current Audacity can do all of that, except it can only extract audio from video, and will need some solution for the pedal to deliver mouse clicks or key strokes.
Please explain what that means.
Sometimes Audacity developers will do contract work at commercial rates, if the software you want is open source. They will not build a proprietary app for you and they will not build a program that encodes video.
We need a software where client will upload audio/video file which will be encoded to specific format (which cannot be played on any audio/video player or transcription software i.e. Express Scribe). The server will have 2 versions of uploaded file. One is original file that client uploaded and second is encoded one. We will share this encoded file with users. Now users will have the player which will decode the file and can play it for transcription, using footpedal.
I hope this information is enough.
What would be approx commercial rates of Audacity developers on contract basis?
If you are uploading to a web server, Audacity is not suitable for this without substantial modifications. It could perhaps be done most simply with mod-script-pipe ( http://manual.audacityteam.org/o/man/scripting.html ) but you would need to address the significant security issues involved.
We get requests for Audacity to be used on web servers every week. None of the developers have been prepared to take this kind of work on.
You can search Google for top C++ programming rates.