I like that idea! How about no damage when ensnared, but 1d4 or 1d6 each time the victim attempts a Str check to escape?Do the throny vines do HP damage?
Still, most of these features are usually hidden by the plate-mail armor that they wear under normal circumstances, and even the wing-spines that come out of holes in the armor’s backplate can easily be mistaken as longer versions of the artificial spines covering the rest of the bramble’s armor.
Well, if we want to boost the AC, we could make a unique armor, like the 3.0 version.
I'm not quite sure I get the spined defense on these. A hand-held short sword wielded by a Medium creature shouldn't really expose the Medium attacker to the spines, should it?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.