IMO you will want a mill. I think you can drill the through-holes without a mill, you do everything on a pedestal drill:
centre punch
spot drill
drill undersize
ream to 12mm (or whatever final size is)
But you also will need a counterbore or a taper I assume, which will be difficult to do, you can get counter boring bits with a pilot that will be a close fit to the reamed holes, but on a pedestal drill it will chatter like crazy and may even send things flying.
tl;dr buy a mill buy a mill buy a mill buy a mill buy a mill
