The issue I think with most estate planning is that your typical trustee won’t have a clue what to do with bitcoin. Probably why most of my clients with substantial stacks use 2/3 multisig solutions like Unchained, Casa and Everlasting for estate planning / inheritance purposes.
Discussion
Your beneficiary/lawyers/accountant would be trustee(s) presumably, and you need to educate them how to access it. Assuming you die a long time from now, it will be well known how to use multisig imo.
The other purpose of trusts is to also preserve privacy, whereas having it at a custodian would certainly expose you to US controls.