One of the problems seems to be determining exactly what ffp rules are trying to address.
I still think the original and continuing reasoning was to prevent clubs sending beyond their means and jeopardising a clubs future, very much following on from Portsmouth's fall from the premier league and subsequent financial nightmare. As the riches on offer from the premier league get ever greater, the temptation for owners to push the financial boat out in the quest for promotion gets ever stronger and this makes the need for financial control even more important.
Bolton is the latest example showing why clubs need some sort of external protection from themselves. While Bury have never been in the premier league, their owners stated desire to get to the championship was behind their financial problems in overstretching themselves.
Many fans think ffp is there to create a more level playing field. While it doesn't do that, perhaps the issue of parachute payments needs to be addressed somehow because the imbalance parachute payments creates that you point out is, effectively, causing other clubs to spend more just trying to complete with those clubs that have the additional spending power that parachute payments give them.
Despite parachute payments giving relegated clubs a marked advantage over the rest, that is still not enough for some clubs, as some ( Villa and West Brom are examples) are effectively spending the whole 3 years worth in 2 years, by borrowing against the third year's fund. I think it is pretty clear that had Villa failed to gain promotion they would have been up **** creek without paddle , and possibly not just as far as ffp is concerned. It is almost becoming the case that rather than giving relegated clubs a financial buffer to make the adjustment to the championship more manageable, it just becomes a war chest/fighting fund for a quick promotion, but with huge risk attached if that fails. Perhaps this is why parachute payments need to be looked at within ffp,