Feature summary (what you would like to be able to do and where):
preloadtemplate= would be similar to preload= with the difference, that it automatically creates what would otherwise be loaded from, let's say, Template:Example/preload by taking Template:Example's required parameters from the template's TemplateData. Needs TemplateData enabled to work

preloadtemplatefilter[]= would—when provided additionally to preloadtemplate=—overwrite preloadtemplate= so that not the required parameters from the template's TemplateData are used but the ones provided by preloadtemplatefilter[]=. I imagine this to take required and/or suggested as values, with required being the default value.

preloadtemplateparams[]= would—when provided additionally to preloadtemplate=—overwrite preloadtemplate= so that not the required parameters from template's TemplateData are used but the ones provided by preloadtemplateparams[]=.

⚠ preloadtemplatefilter[]= and preloadtemplateparams[]= might not work when combined.

Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):
Often times (though, not always), there's no need for custom content to be preloaded but merely a specific template (I mean, why not utilize what we already have)

Benefits (why should this be implemented?):

• syntactic sugar for doing this manually via preload=
• quite intuitive, especially for users using this extension for the first time
• less error prone
• make updating a separate preload template every time, the template it is based on changes