Well I've almost finished doing exactly what you're proposing. Because of the day job, I've only been able to have lessons part time, but it's worked very well. I find I can use some of the CPL time to brush up flying skills for the FIC (e.g. PFL's, stalling etc) and with the instrument time on the CPL, with my IMC already earnt, I'm in a good position to move on and de-restrict myself for the instrument instruction (once I've completed the additional 5 hours and g/s)...
Regards
glush