One answer is to increase the values of all your health and damage so that you're never dealing with numbers less than '1'. The armour's quirks will never bother you, then.
Alternatively, there is effect 28, which could be used to make something using normal bars.
28=bar parameter1 increased by bar parameter2 * parameter3
The problem is that is multiplies instead of dividing, so it's difficult to use it to do more damage the lowe another bar is.
So what you could do is put your shield bar in reverse. The higher your shield bar, the more shield damage they've taken. You might have to call it something else, like 'Shield Overload', or something.
When an enemy laser hits you, it adds a specified amount to the Shield Overload bar, and takes away an amount from your Health bar equal to your Shield Overload bar multiplied by a number.