I want to simplify and tighten the interface for upload for admin editors, both in the tinymce editor button and the add files menu page.

Is there a quick method ( which is upgrade friendly)
OR is this getting quite heavy duty development?
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Ideally I don’t want to just hide elements with CSS.

Hide fields
I have custom fields populated with information but I don’t want the editor to see those once the site is live.
I only need my custom styled templates.
I also don’t need language, version and a few other fields.
Hide some tabs on the tinymce button..

Move fields
Permissions should be available more easily. ( they are on the extended form but I need them more readily available)

Defaults
I want to set defaults for templates.
So… limiting how much the admin person has to choose and think. ( too many choices and they make mistakes)
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CSS in admin
I want to style the form upload. The form is very long and bulky and could be more styled and more compact.

What would be the upgrade friendly styling methods ?
Any guidance much appreciated.