induction fan modification on boiler

I have a Jensen wood boiler with a bad indution fan. Since I have to replace anyway I was thinking of mounting it remotly and pushing the air through a heat exchanger to pick up heat from the smoke pipe. I was thinking of stainless steel flexpipe running along smoke pipe with a metel shroud covering them both. It would be kind of seton like in theory. Maybe I could push 200* air into fire instead of 60*. The only issue I can think of is restriction of pipe reducing cfm and how much of a fan will it take to overcome it. The origanal fan is mounted directly and is rated at 60 cfm. Can anyone think of any reason not to do this? I have never used the boiler before so I have nothing to base performance on. Thanks in advance.