You know, I can't find a "repeat underpayment penalty", though the IRS does have a "negligence or disregard of the rules or regulations penalty" so I think if you tried to pay 100% on tax day you may end up paying more than Bitcoin appreciates/holds purchasing power during the year. I agree Bitcoin is likely to be a better place to hold that 10% for the year.

There's a statement when you fill out a W-4 that amounts to "I affirm that this should net to roughly zero at tax day" and they'll likely point to that when you try to not pay incremental taxes.