Do you care what the other 'half' is?

[Arkhios]

Personally, if I were to allow non-human halves (I'm not saying I wouldn't; this is just hypothetically speaking), they would still use the actual race's traits (e.g. aasimars would still use all aasimar traits as normal, regardless of their other racial half), except where it makes sense to alter due to their racial build.

For example, a dwarven aasimar would have a land speed of 25 ft., and their speed wouldn't be reduced by wearing heavy armor.

Likewise, a halfling aasimar would be small, have the same 25 ft. land speed, and perhaps halfling nimbleness as well.

But I'd look at each case individually.