There are some obvious parallels to take inspiration from, but I think it may be more instructional to consider the differences. What are the areas of the garment that might benefit from the rigidity/shape of a steel plate and where is it best to let the cloth be itself?

There seems to be a middle ground too, where the cloth is somewhat restrained but continues to behave as cloth...

Patterning the suit of armor makes more sense to me than patterning a tailored jacket. I guess that's why I am here!

Concave shoulder line, roped sleeves and do I detect high armholes too? Back when bespoke meant bespoke. Jokes aside I'd love to see what sort of patterning would go into that, I'm sure I've got a book somewhere about the construction of old suits of armour.