Update: This idea is currently not planned based on our program planning and prioritization of all Tridion Sites ideas for early 2018. We may revisit this and other great ideas based on more information and additional votes.
Notes:
GetTemplateFragment only applies in the context of templating, so any changes would not change this method. But I added text to the original idea to make it clear the request is about ECL previews for editors. This would be in the context of editing and selecting items.
The existing ECL functionality does allow editors see ECL images and thumbnails for videos, but not a full (video) player directly in the rich text format area. Editors can, however, see rendered ECL items using their Staging environment or with Content Manager Explorer Preview, depending on their templating logic.
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