This is in no way an area that I have any knowledge of, but applying what I do know
I would want to see how that £40 000 is broken down. So how many sessions, per subject, does that cover?
Are the tutors subject specialists? So will your daughter be getting the same level of teaching that she would in mainstream school?
Does she not need to be working with other students on any of these GCSEs? How will they facilitate discussions etc?
Does the school have any experience of this set up? If so, what are their views?
What are their views anyway? Are they in favour? Can they foresee any problems?
Do you have any experts working with your daughter? Are they in agreement that this is the best way to meet her needs?
I have no experience of this and so it might be that it is a common place set up in special schools and one that works well.
My gut feeling though is that £40 000 doesn't buy you much in the way of teaching hours for multiple GCSEs, if you look at how many hours they get in mainstream school, per subject. Although as it's 1:1 maybe you don't need as many hours.
I think I would be talking to school to see what their view is on this and then go from there.
Are there any organisations that can advocate for you in this instance?