Mike
You say your debt is 'above the norm', so lets assume you could actually find a bank to lend you the funds (given the current credit crunch) to complete the CPL/IR/MCC, your living costs whilst training and funding the continuing repayments on your existing debt commitments. Have you actually calculated your financial position once all of this is completed? Don't forget the contingency costs for partial/failed CPL or IR skills tests and the necessary additional training/re-tests.
Now assume that having the licence/ratings, you can't find a job (very common for modular pilots). (I know quite a few folks who obtained the 'frozen' ATPL only to find no jobs and with no funds to go further. They have gone back to their old jobs and with the debt to repay from training could not afford to stay current let alone build hours.) Will you have the funds for an FI rating and would you be able to service your now sizeable debt whilst earning very little from full-time flying instruction?
I don't want to rain on your parade, only ask you to work through the financial calculations using a worst case scenario. Only by doing this can you decide if this is a risk which is worth taking.