The scope is the same of what was discussed here but with different circumstances: my head was fired and replaced by a colleague of mine.
Is it wise during a salary raise negotiation to mitigate possible discussions about company's economy problems by arguing about the salary originally planned for the dismissed head ? My point would be that the head was planned of course to stay in the company and withstand as well the economy problems, so now since nobody else will be hired to replace him (my colleague took physically his place), that salary represents a saving for the company and enough to raise my colleague's salary and mine (in the intended proportions of course).