Personally i would try and get an old cheap sink of same the construction to give a few trials on.
How to grind ceramic sink.
If the porcelain is coating cast fe and the sink bottom is flat you might consider a mag drill.
It will grind down a ceramic tile or object with precision.
Start out very slowly with the grinder set on a medium speed until you can get a feel of how fast the tile will grind.
A ceramic grinder uses a metal aluminum oxide or similar grinding wheel this is a wheel that has sharp metal flakes of aluminum oxide glued to the surface much like sandpaper.
Install a porcelain tile grinding disc on an angle grinder.
Porcelain sinks seem to have a paradox about them.
The good news is that drilling the initial hole is the most difficult and riskiest part of drilling into a porcelain sink.
Use small grit for a more mirrored finish and larger grits 120 and up for rough grinding.
As far as chipping just go slow and deal with what shakes out.
Step 4 gently apply pressure with the grinding disc to the tile surface.
Set a water filled 1 gallon milk container next to or above the hole.
Just for my info how much material has to be removed.
Ceramic is a very hard material and you need special tools to grind it properly.
One person suggested to get a dremel and cut away the rim from the retaining nut without removing the sink less work someone else suggested to take the sink out which means cut the sealant and caulk remove the wood holding the sink remove the piping and cut it with a tile cutter.
Place a plastic bucket under the hole you need to enlarge.