我想"衛護(wèi hù)"的"護(hù)"是由"辨護(biàn hù)"演变而来的。I think "護" in "衛護" is derived from "辨護" (verbally defend) and hence the 言 radical. This is what I found on 汉典:
(Sorry, I can't decipher the full text for you. Maybe someone else can help to explain what it all means.)
"衛護(wèi hù)" means to protect or defend, so you are right to point out that 言 radical should be changed to ⺘radical instead. This is reflected in the new 简体字 "卫护".
"擭(huò)" wasn't used as it possesses the meaning of capture: