Would you give Fortress Defense to a +ATK Lukas?

I have a Lukas (+Atk too) but haven't thought of a build yet. I was thinking this to use him as a lure but I don't know if it can help you.

If you have the resources, you can try Close Defense 3 with Quick Riposte. This way you can lure melee units to attack you (giving you a +6 Def buff) and QR gives you a follow-up attack regardless of speed.

You will need to use a Silver Spear to maximize the damage you deal counterattacking, also a Hone Atk/Fortify Def buff will make Lukas more bulky. Threaten Atk 3 and Escutcheon will make you even bulkier. He won't stand a chance against ranged units, specially if they're mages so be careful. Having a healer is also helpful so he can survive more turns (also to activate QR effect).

Earth Boost could help if you use an HP seal. Also using a healer or pseudo-healer will keep Lukas HP high for the Def buff so it could work.
Fury will give a bulk to every stat, even if it's overused it could work too.
HP/Def 2 adds more bulkiness.
Armored Blow 3 (Def +6) if you're the one attacking.
Death Blow 3 if you're using a Brave Lance.

These are the ones I think could be useful but it's up to you, hope it helps.