I never mentioned a timer, simply a recast on the ability so you could not switch from one party member to the next as you please. Also, With your method, everyone would just simply need to hid behind the paladin; there's no need for hate holding abilities then. Basicly all the paladin would do is stand there w/ auto cover while the whm regens and stoneskins the party. This is also terribly exploitable by ranged jobs/class.

For an idea to be considered by the developers, one touch base with them and provide a ballanced idea that also considers other classes which may also share a similar objective role.