Is it possible or has anyone ever requested for amendments to be made whilst a project is under con? Ie like plumbing changes or not putting up a divider wall. Or does it have to be delivered as per original form?

I feel it’s wasteful to use materials for something you know you’ll dismantle anyway.

Pay for any extra work that needs to be done or in this case relieve them of having to put a partition wall say between the yard and kitchen. This is just an example.