if you use the same name a second time the second one takes preceedence.
you cant delete stuff you can just overwrite them, but for the purpose of your question thats the exact same thing.
creating similar scripts
This is how you overide factory functions. What you do is you just make a script that has same name and same procedures and put it in a folder that has higher priority in lookup. In other words your own script directory. Thsiway you never need rto delete anything.
And you can prototype stuff by just redefining functions in the script editor. Most maya scripters do this all the time.