gg, basically it´s difficult to help here, because no one was in such situation. You should primarily ask Fidelity for options and/or contact the WMILT.
My wifes was as well in TRUST and my kids opened accts and the TRUST(I) transferred their respective %'s put in their accts..........I would though SUGGEST staying in the same brokerage co as many probably don't want the headache
Normally a Trust is an on-going entity, once the grantor/trustee passes away there is a successor trustee that takes over to act on the account and you could possibly leave the assets in the same Trust account.
There are many, many types of trusts and you should talk to fidelity directly.