For example my py script already has one instance running and when I fire another instance with args, instead of allowing the new instance to run, make it pass its args to the main instance or make it so the main instance awares of the args so it can do whatever it needs to do with the args. Is something like this possible?
It is possible but not trivial because the processes are unrelated. So you have to set :

an exclusion mechanism (file lock should be portable across architectures) to allow a process to know if it is the first - beware of race condition when a server is about to exit when a new process arrives ...
the first process opens a listener - a socket on an unused port should be portable
you must define a protocol to allow you processes to communicate over the socket
when a process discovers it is not the first, it contacts the first over the socket and passes its arguments

So it can work, but it is a lot of work ...
There could be solutions a little simpler if you can limit you to a specific architectur (only Windows or only Linux) and make use of specific libraries, but it will nether be a simple job.
Python - Disable multiple py script instances and pass their args to main instance