Vulnerable persons trust with multiple settlors

I am acting for a client to who set up a vulnerable persons trust for their son.

They have also recently inherited from an estate and wish to enter into a deed of variation and have monies added to the trust already set up so that they do not need to open further accounts and can keep all of the funds together.

As it is a VPT, the usual relevant property rules do not apply, so I am unsure if there are any downsides to doing it in this way.