Vectoring for Visual Approach
There are no restrictions against vectoring from us ATCO.
As you said there's nothing keeping ATC from doing this, but my very argumentative colleagues put the definition of visual approach on the table so that's why I had to ask.
You appear to have either done some thing which your colleagues find an issue with and possibly feel its unsafe.
or
You are suggesting something which your colleagues find an issue with and possibly feel its unsafe.
Either way the internet will not give you the local/national answer you are seeking.
Your choice is simple.
1 Ask your OJTI.
2 Ask your Local Management.
3 Ask your Safety regulator.
4 Ask your National Supervisory Authority.