We have a task to organise the crypto custody (the storage for large amounts with multisig, multicurrency, key-recovery and other features). We have preselected BitGO, but before making a final decision we’d like to collect feedback.
Have you ever worked with BitGo? Can you leave a feedback? Or suggest an alternative?
Your question seems to show some ignorance of that true nature of crypto currency. This is pretty common.
Bitcoin is held in private keys. These are no more than 50 some digit numbers in base 58.
Translating, your question becomes "How do I safely store a 50 digit number?"
The general answer is to split it up and encode it and place the pieces with several parties.