Phil
What you are proposing will end up being a pretty serious expenditure of effort and money. Unless you have suitable material stashed away a new column won't be cheap and making a new spindle will be a fairly serious undertaking. Need a decent size, accurate lathe to do the job easily. Then there is the wind-up mechanism mentioned by David which is pretty much essential for a floor mounted metal working drill. Partial offload of table plus tool weight by either a gas strut or simple hanging weight is OK on wood working drills but doesn't work that well with the generally heavier stuff involved in metalworking.
Had a Pollard Corona type primarily intended for woodworkers having a hanging counterweight which came close to OK. But the table ran on box ways and was very heavy giving less relative change in weight when work was mounted up. Box ways stopped the table twisting so heaving up didn't upset the alignment. I feel that on a round column you'd never get it straight again after moving up if you don't have mechanical lifter. Whether the common rack and handle type or Pollard style double screw-jack.
Finally, although the Star is a more than decent quality drill its the big 7-Eight and 10-Eight that are the standout floor standing versions. In my view about as good as a round column floor standing drill can go.
If the price is right buy it, use it for now and be prepared to trade up when the right machine comes along. Always a ready market for good quality bench drills at acceptable prices. Floor standing ones, especially hefty floor standing ones can be hard to shift. My Pollard 15AY cost me £100 plus collection which, objectively, was silly.
Clive