Speaking from the industry side, the basic issue is that the customer can’t have it both ways.
If you don’t pay the balance, you are effectively choosing not to travel, so you lose your deposit. A lot of the smaller companies are saying balances can be paid later than usual, but the big boys aren’t able to offer that sort of flexibility due to the sums involved.
If you pay in full, you’ll get your money back if you are unable to travel, so assuming you’d be happy to travel if the government say it is safe to do so, there isn’t anything to lose by paying in full.
A third option is deferring the holiday to a later date. Most smaller companies are encouraging this as it keeps the revenue in house, so it might be worth a try if you can speak to someone? Again, the big boys may not be doing this though?