Instead of MeshDeform (which is made to work in volume) try Surface Deform with very simple lowpoly “proxy” mesh for lower part of the jacket. (Also, create a vertex group for the lower jacket). After the modifier is initialized, create a shape key on a proxy mesh and pose it in Edit mode (If Surface Deform fails to initialize, triangulate the "proxy)
Alternatively, there is Cloth brush and Cloth Filter utility in Sculpt mode. Lets you pose cloth without setting up simulation, though I do not have much experience with it
i tried that surface deform but the jacket is too open to get it right (like meshdeform) haha but i tried the cloth brush you mentioned and somehow i kind of nailed it. the only disadvantage is, i have to separate the parts and manually realign them all. but it works!! i know about the cloth brush tho but didnt explore enough and it has these deep mechanics xD