Tricky tile removal/replacement

[Michos]

I need to cut a small piece of discolored tile from a larger section at the entrance of a shower floor. Ive attached an image. Im unable to cut along the grout lines on either side because, as you can see, the tile runs underneath the glass which cannot be removed at this time. Im wondering if anyone has ideas on a tool I may use to get a clean cut on either side of the discolored section. Obviously an angle grinder is only going to be able to cut so far down before damaging the tiles on either side. Im thinking that an oscillating multi-tool could work but im concerned that the standard bit for removing grout is going to have a hard time going through that much material and will not be so precise. Any ideas on what tool, bit and/or method I should use? Of course, to complicate the issue, im sure that there is a shower pan underneath the tile so I will need to be extremely careful not to damage it.

[Davy]

I would wait till the glass can be removed. No way would I cut and pry on any part of the curb/saddle with the glass in place. Then, if possible, I would want to have some extra marble and mosaics before starting. Knowing what type of pan was used would be helpful. Something needs to be done but I'm sure you realize you could be opening a big can of worms.

[Just In Tile LLC]

I second Davy on can of worms, all the modern systems don't play well with isolated removal.