Witnesses typically scale up over time. If you're a backup, you can front a fixed cost of less than $1000 and run it on your home internet. This is reasonably stable enough nowadays. When you get higher in the witness ranks you can deploy more nodes and improve redundancy and performance.
Missed blocks from one entity on the network won't impact things significantly anyways, we have built in redundancy at the system layer (the blockchain itself) so it really isn't a practical concern.