I agree that that is not an ideal time.
a) its probably the steepest 'step up' you'll ever experience in terms of responsibility so being away for 3 years beforehand is not ideal.
b) If you do it post-FY2 you can do infrequent locuming alongside your PhD. This will both help your bank balance and hep keep your head in the game clinically.
c) I understand the pay deals can be better if you are already in practice. I do not know much about how this works though.
d) It is possible to get into neurosurgery without a PhD if you've already got publications etc. What you could do is apply to neuro whilst organising a PhD, if you're unsuccessful go for the PhD if you're not get your foot in the neuro door then do a PhD later.
If you are gunning for neurosurgery you are already, presumably, in contact with neurosurgeons trying to get publications etc? Why don't you ask them?