Control loop for CD player

We have a PIC based control loop for a consumer audio product we need designed. The control loop handles standard commands one would expect for a CD player: play, pause, track select, etc. What makes this difficult is the control loop has to interface with an existing player platform the product is based upon and the two systems communicate over SPI - the host system can be slow. We have a poorly written version working in an existing product that we want rewritten with good code not riddled with timer loops and spaghetti hacks. The project should take 4 to 6 weeks and hired programmer will have both access to the hardware as well as our internal engineering team.