If the tailstock of your Atlas can be offset enough you can cut the tapers by centre drilling the ends then cutting one end at a time by turning between centres, offsetting the tailstock to get the taper you want.
If the tailstock doesn't offset enough you do the same as the above except you use a boring head (usually used in milling machines) with a conical centre in place of a boring bar, offsetting what you need for the tapers.
Once you have made your blank you could cut and silver braze HSS blades to it like you were thinking. Or if the amount you want to ream is minimal (or you step drill the hole first) you could cut the long taper to make a D bit. You'll have to harden the tool so the cutting edge holds up.
Never done any of the above myself but in theory it works perfectly.
Pete
