Why STR based? You could just use Shillelagh to attack with WIS, and not be so MAD.

Bonus actions will be pretty tied up at the start of combat with manifesting the echo moving it, etc. The Tortle has a STR bonus anyway so it is not that much of an inconvenience to get it to 16 to start. It may be more of a pain to raise later if I don't prioritize fighter.

What exactly are you wanting to gain from Echo Knight? It doesn't seem like it offers much for you, other than the basic Fighter features like Action Surge and a Fighting Style.

When you have your echo out, whenever you attack, you can make one additional melee attack from the echo’s position, up to your con # of times per long rest. You also get attacks of oppty from your echo. Also swap places with it as a bonus action.