Is there some way to extend Mathematica's dimensional analysis? For example, I'd like to be able to provide it with dimensional equations like energy=mass with units scalings like c^2 and have it extend the possible interpretations in terms of target dimensions and/or units.
Although my question is more general, the aforementioned case is supported by DimensionalCombinations if you provide the additional parameter IncludeQuantities -> "PhysicalConstants" with this example:
DimensionalCombinations[
{ QuantityVariable["E", "Energy" ]},
QuantityVariable["m", "Mass"],
IncludeQuantities -> "PhysicalConstants",
GeneratedParameters -> None]
which produces these possible interpretations:

PS: I'm aware of this answer providing a kludge to extend units conversions but it isn't clear this will also extend the function of, for example, DimensionalCombinations and, in any event, I would hope for something that isn't a kludge. (And in any event, the code in that answer doesn't work on my cloud notebook copy. It produces an error upon executing the test.)
GeneralizedUnitConvert[....]which defaults to the usualUnitConvertwhen it has no special rules for the given inputs. – Jason B. Aug 30 '22 at 18:39