Pass SDK options down as `readonly`

[lforst]

As discussed with @timfish in #5203 (comment), we were contemplating whether it would be a good idea for the SDK to pass options down as readonly. In that particular case it would have caught a bug, and might also do so in the future.

This is non-trivial of course, so we can just use this issue as grounds for discussion before actually starting to implement this.

(Just a random thought: This could be done as a hacktober PR)

[HazAT]

I would not do it, there are certain edge cases where this hacky approach just fixes things for certain users.
Closing this avenue just makes everyone's life harder.