Since the wiki has gotten to an appreciable size with a pretty impressive number of pageviews (25 million), it's time to add a little process to our editing work. For templates that are used on a lot of pages, it would be best to have a discussion about major changes you'd like to make to the template before making the change. Just a quick one to see if the rest of community agrees on your change would be good enough. If there isn't agreement, work out a consensus.

This is also important in light of the wiki issues where templates do not always update on all of the pages where they are used and may not update until that page is edited. Changes to a widely used template can also make the wiki slow for a period, so making your change via one edit is currently preferred.

For testing purposes, you can actually create a mock template in your User: space. If you want to create a mockup of your suggested changes for a template, you can just copy the original template and put it into something like User:Equinox/Testwhatever. Then you can use the mockup on something like User:Equinox/sandbox by using {{User:Equinox/Testwhatever|Blah|armor=blah blah}}.

Starting a discussion is also a great way of suggesting a change to a template even if you don't know how to make that change -- more experienced editors can help you learn how code what you're suggesting.