Too large wall niche in shower - solution?

Hello,

we would like to install a recessed wall niche in the shower of the bathroom. For this we had ordered a built-in metal wall niche from Hansgrohe. Problem: There is a plastic insert for the built-in wall niche, which would have to be placed in the hole, then sealed around the edges and tiled over. Only after that would the actual box be placed in the plastic insert and sealed again with silicone under the edges on the tiles. Now it is the case that the area around the hole has already been tiled and unfortunately the hole is also too wide (see attached picture).

What possible solutions could be considered now? And the following solutions are running through my mind:

[*]Remove tiles around the hole, make the hole the right size and install the box as planned and according to the installation instructions
[*]Cut a larger hole directly in the wall and install a larger built-in niche. This would be without a plastic insert and would be fixed directly with tile adhesive in the hole and silicone would be applied under the edges that lie on the tiles. But what I am wondering is: How can the silicone be renewed later? Because the box is firmly anchored in the hole with the tile adhesive. With the Hansgrohe solution you can take the box out of the bracket at any time and renew the silicone under the edge.
[*]Tile over the hole afterwards (the question arises whether this can be properly sealed?)

Which of the three options would be feasible or which arguments speak for or against the individual options? I would be very happy to receive advice!

Best regards

No matter how you do it, it will only be guaranteed watertight if the existing tiles are removed and then a seal "around the corner" is applied. It doesn't matter whether with a box or with foil (like floor/walls). "Only" with silicone is a no-go – even if it might hold tight. But if not, you will regret it.