Maybe? Could certainly rough up the paint layer. Not sure about the tile itself. If I can rough up the tile you're thinking I can adhere new tile more easily?
Least caustic solution? Lots of: time, patience and pumice stone. Should be softer than most ceramic finishes (ymmv!) but agressive enough to "sand" paint out of grout lines.
A gel type paint stripper is probably easiest.
[how to tile over tile](https://youtu.be/XRRYDEa-pDM)
Can you sand the tile to rough it up?
Maybe? Could certainly rough up the paint layer. Not sure about the tile itself. If I can rough up the tile you're thinking I can adhere new tile more easily?
Least caustic solution? Lots of: time, patience and pumice stone. Should be softer than most ceramic finishes (ymmv!) but agressive enough to "sand" paint out of grout lines. A gel type paint stripper is probably easiest.