I'd say it's an interesting project to try, but I would temper my expectations for the results.
Problem is I can't even disassemble the phone cause I know I would break it when I get to the adhesive, that's what happened to most people who tried to disassemble it, terrible industrial design.
So the only way is to cut or melt a section of the plastic back off which also kinda destroys the phone (but only aesthetically). I would do this in a heartbeat of course if I had the assurance that it would cool the CPU.