As old camelback drill presses go, the table is not destroyed too badly. On this 'board, we've seen some tables that looked like a lunar landscape with little iron remaining at the original surface/height. There is some damage to the table on the Royersford DP in this thread, but nothing so bad as to prevent it being used as it is. As long as there is enough of the table surface remaining so a vise or work piece can span the "craters of the moon", the machine is usable.
A quick fix is to stone off the table surface with an oil stone, then place a piece of steel plate on the table. Of course, if the plate is just hot rolled steel plate, its flatness is hardly going to be of machine tool accuracy. Stoning off the table surface and using drill press vises or hold down hardware ("jewelry") such as tee nuts, studs, slotted clamping dogs, or C clamps will still work despite the condition of the table.
Repairs to the table are a function of how much the new owner of the DP wants to spend. Getting a new table cast and machining it is the extreme high buck end of the spectrum. Getting a piece of steel plate as a round "burnout", fully annealed, and having it Blanchard ground is still towards the high buck end of the spectrum. A disc of steel plate, Blanchard Ground and fastened to the existing table with socket head capscrews in counterbored holes would give a new table surface. Rather than tee slots, a series of holes (drilled thru the new plate and continued thru the old table) for clamping bolts, and a series of tapped holes would be the alternative to milling tee slots.
To fix the old table, a few options exist. Some are purely cosmetic and might actually work. Using a "repair resin" such as Belzona or Devcon to fill the holes could be done. These repair resins are formulated with fine iron or steel particles in them and are advertised to make repairs to various things like pump casings, valve bodies, machinery castings, etc. To hear the manufacturers of these products tell it, they can repair anything short of a broken heart or thw crack of dawn. Of course, these resins are pricey. When they pull out of the hole or crack they were supposed to plug, the salesman or tech support guy invariably says: "You failed to adequately prepare the substrate". Cleaning out the old holes in the table and running an air needle scaler or localized abrasive blast is what it would take. The repair resin people invariable say: "Prepare substrate by abrasive blasting to a frosted white metal surface" and will disavow preparing the substrate by wire wheeling, solvent washing, grinding or using burring tools.
If the purchaser prepped the unwanted holes and filled them with Belzona or Devcon repair resin, the surfaces could be spot-sanded with an auto body sander or die grinder to get things almost flush. Draw filing would finish the fill job.
The biggest hole might be plugged by boring it to a consistent diameter, then turning a steel plug with a flanged end. The flanged end would seat against the underside of the table and be fixed in place with some capscrews. The surface of the plug would be ground down using an angle grinder and discs to get it close, then drawfiled and possibly hand scraped to match it to the surface of the table.
The tee slots present a real problem. Depending on how much meat is left in the casting at each tee slot, a repair could be made by "inletting" pieces of steel into the table to replace the tops of the tee slots. This would mean having a vertical mill big enough to handle the table, and machining "inletting", similar to a carpenter "letting in" the butt of a door hinge. By using steel flat bar and socket head cap screws, the broken or drilled-out areas on the tops of tee slots could be replaced. Again, it would mean either taking a skim cut on the table to get everything flat including the "repair pieces", or resorting to the angle grinder, followed by a straightedge, drawfiling, and some hand scraping.
This last fix, depending on how resourceful a person is and how much time they want to put into it, is probably the low-buck end of the spectrum.
Build up welding or brazing of the broken out areas of the tee slots would not, IMO, be an option.
