Like?
PlayerStandardArmor
maxUnderwaterForwardSpeed = 8.4;
maxUnderwaterBackwardSpeed = 7.8;
maxUnderwaterSideSpeed = 7.8;
Either way, it's part of the system, it should remain part of the system.
And since that support script doesn't look like it's going to support individual values anytime soon, I think the next step after adding water/all values would be to add VCE support, like, <var:pl:maxForwardSpeed>, which will call the get/set function depending on whether you're using get or set.