I was just double checking, and the wording of pact initiate seems that you don't actually get a pact that way (you get the pact's at-will, and qualify specifically for paragon path's requiring that pact, but it doesn't actually say you gain the pact).
I was actually thinking the same thing, as it would have made it possible to do weird builds for various E-classes (a half-elf knight, for example, that uses a pact blade and thus charisma for all his MBAs; not to mention a thief that can pick up a +3/d10 light blade) but I don't think you actually get the pact unless you are a 'true' warlock (or at least hybrid). [the Binding Initiate seems to function the same way, giving you things associated with the pact, but not giving you the pact itself].
Seems they may have caught it (or just avoided it accidentally), as there doesn't really seem to be an easy way to mix the pact blade + associated MBA with the Eclasses that riff on MBAs themselves. The closest would be Executioner/Warlock hybrid, which would have some fun, but the only tricks Executioner's do with MBAs is the bits of striker damage, compared to stuff like power strike, backstab, the various stances, etc that the other Eclasses have. They still may want to address the Executioner issue.