If the person became unwell or was unable to manage the trading account for any reason (other than death) the person acting on their behalf would have to have a Power of Attorney (PoA) granted. This is not something that Fusion has any part of, it will be done within their local jurisdiction and is an official government process, which as you would expect is a lengthy one. If something unfortunate was to occur where someone else would have to act on the Fusion Account holders behalf, they would need to provide this.
Importantly, this still wouldn't give them authority to say withdraw fund to an account in their own name, they would simply be acting on behalf of the account holder and could move funds out of the account into an account within that persons name (the account holder with us).
The process is different in the case of a death. If an account holder with Fusion was to unfortunately pass away, someone would have to reach out to Fusion and provide an official death notice for the Fusion Account holder, along with official documentation to show they have been named as a beneficiary of the deceased's wealth, property or estate. This will then be reviewed and handled by compliance at Fusion.