the biggest disadvantages are that for formatting purposes your forum's editor uses single chars (letters), and not bb tags instead:
... (and many more, to be continued)
Additionally, it is unreasonable that your forum's editor expands links automatically to a preview:
That is not always wishful (actually mostly unwishful):
a link must be a simple link (a text line), and if one wants to make an embedded image or a video preview out of it, then one is free to use the tags for
(again, almost everything of this post again has been corrupted unless that I now reformatted all that belated by code tags!)
Of course the BB code tags should be provided by a menu list via button click like you already do, just using BB tags instead of your single char editing.
IMO switching to a BB forum's editor (phpbb, vBulletin, MyBB) would be the most convenient and the most effective solution.