Would it be good for a pretty much straight Might character using Invulnerability?

yes. Default Might framework is STR/CON. Invulnerability uses STR and CON values.

Bionic Shielding is one of those powers that is useful in any build. Also, you can use it to help other players and NPCs. It has a pretty short cooldown for what it does. Mindful Reinforcement is similar, so you might want to compare the two, especially if you SS PRE.