if you are to usefully exploit at the full height capacity of a floor standing drill you need "some" room each side. Simply sliding the drill into a near minimum space between benches gives you little more capacity than a simple bench drill. As proven by a friend of mine who did just that. Albeit mostly because he had a good floor standing drill and didn't want to mess around changing machines.
He later cut away the bench top immediately adjacent to the drill and installed lift out panels which won more depth down to first shelf level. Not the fastest or most convenient of arrangements but handy when needed. In retrospect shelves on wheels or one of the economy range mechanics cabinets would have worked better. I'd seriously consider retaining the floor standing drill and putting a set of mechanics drawers on wheels alongside it, on one or both sides. Possibly something like this :- **LINK** from US Pro.
Couple of years back I put some similar drawers that had been around in the garage for ages on wheels and moved them into the workshop. Turned out to be far more useful that I'd expected. Should have done it ages ago. Didn't appreciate how useful the move around ability was and how effective multiple smaller drawers are for tool storage.
Clive