When building Marketo Guided Templates, you can build them locally and make use of Marketo's meta tag commands. Now you don't need to insert the template into Marketo to test it. This should speed up template building a bit.
This tool when activated will parse your template file, take the meta tags and switch out the values. Rendering your template correctly as your users will see. This will allow you to test and build your templates while still using the templating meta tags correctly but without the headache of uploading the file and going to the URL.
I have recently moved from Marketing to Engineering. If the value and request is high enough, I will update the extension to allow for input values to be through the browser allowing for another level of live interactions and development without having to go into Marketo. This will easily speed up all template building.