I agree, that it would be great if SC could split up the task into two things, one where we just map maxspeed=implicit by expanding the definition of the maxspeed=implicit tag on roads which it affects.
And mapper with more knowledge or using the SC Expert Edition can then enable a second quest, which asks which explicit speed limit exactly applies it, so it can be mapped with a more specific maxspeed=* tag.
Using a secondary tag for maxspeed, like maxspeed:type=* however makes no sense, it adds redundancies, same for the misuse of the source tag (source:maxspeed=*), since there’s no information tagged here, it makes no sense to tag a “source” here.