port mpkg deliverables for older systems?

[Joshua Kordani]

Greetings all.

I've found that the mpkg created from running port mpkg carries a 
dependency for the minimum OS on which the port mpkg call was made.  Is 
there any reason for this hard requirement?  I had been tasked with 
making installers for older versions of ports and their dependencies by 
cloning specific commits of the ports tree and building mpkg from there, 
but the system that I do this on makes mpkgs that require that version 
of the OS.  I wish to make mpkgs that will install on older version of 
macos, to wit, versions I know these combinations of packages and their 
dependencies support.  Is this generally considered a bad idea? In many 
cases it seems like the dependency installers are simply provided in 
binary form already, because I imagine the risk is that I would be 
building ports on a newer system and naively expecting them to work on 
an older one.

Any advice?

Joshua Kordani