Disabled tenant wanting to install a shower

Other

I have a potential tenant who has viewed my apartment and would like to take the bath out of the property and install a shower (like a wet room). The work would be done professionally as her dad is a builder.
She has also indicated that in the future she would possibly purchase the property. I know the family personally. I have said that that is fine as long as if she moves out she installs a bath once again.
Obviously everything is fine now and she is agreeing to that but would like to try and cover myself.
Shall i put a clause in the agreement stipulating that is she leaves the bathroom has to be converted back? I am able to ask for a higher bond? Should the works be carried out once she has signed the agreement and paid the first months rent?
Thank you for any advice you can give me.
Regards