Why custom ?
All forums, cimments systems have this feature as standard.
Having to this added in near future update, all user can benefit from it.
The way is working now is wring all together, no need to click the video icon and then the hard to find embed YouTube code, plus you need to type some text ... Having just the embed video code doesnt work as the system thinks you havent typed any text.
By using the youtube url for the video not only you save clicking on the icon but also having to type some txt next to it.
If i only need to post a video, why would i need to type some txt too?
Youtube embed video codes it's a thing if the past... Thats why it's so hard to even finding it on YouTube website.
Thanks ;)