Yes, it's possible to drill the rim (assuming it's aluminum), but before you do so, make sure the rim is wide enough to handle the width of the valve + two thicknesses of the tire bead. Looking at the rim (picture) I suspect it'll be very borderline. Width considerations are a major reason that bicycles use Presta valves.
I suggest you simply stick with Presta valves and simply leave O-ring adapters on them full time.
As for the drill size, I believe it's 5/16" but measure a valve to be sure.
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