(I’m not entirely convinced I understand you correctly, but this is my answer:)
That is why you’ll have to include the Checkmk version in the name of the package. Once you’ve uploaded “Bar Extender 2.1.3” you cannot upload older versions anymore - the lowest uploadable version will be “2.1.4”.
You can have “Bar Extender (Checkmk 2.0) 1.0.3” and “Bar Extender (Checkmk 1.6) 1.0.4”. But it would be wrong to claim that one is a later version of the other one; they are packages in their own right, and can be upgraded independently from one another.