I know from personal experience that getting a Poser only morph into the DS4 version of Dawn 1 was a lot of work, I have the knowledge and skills to do it, but a good 99% of the DS user base doesn't, especially if they don't have a copy of P9+.

Can't DS import a morph from an OBJ (same vert order and face defs as the original)?  The same way Poser can "load FBM" from a file?  In Poser you can do this either with a morphed (but split and Poser vert ordered OBJ) or a morphed version of the original mesh.

If so, then it's easy, no?  Export the morphed mesh in either app as an OBJ then apply/import it in the other.

Also, when creating custom morphs on an un-morphed figure, wouldn't you just import that OBJ into (say) Blender, sculpt it, then export the OBJ back out and import that?  Blender keeps the vert order so long as you don't change the vert count (split or weld).  

According to my testing, this seems to work because poser splits the same OBJ the same way every time.  If you bring in a poser ordered OBJ, it's already in the order poser needs so it works.  If you bring in a OBJ with original order, then it splits it the same way it did when creating the figure which produces the same poser order, so it works.

The difference is outside: sculpting a split mesh es no bueno.  It tears.

Anyway...

If you want to *further* morph a Poser morphed figure, you can export that OBJ and use a script (I have one) in Blender that applies the Poser vert ordered OBJ exported shape back onto an original vert ordered shape.  Takes about 1 second.  I can either make a new OBJ from that Poser exported mesh, or APPLY that shape as a shape key to an existing blender OBJ (imported original OBJ mesh).  Then export whatever shape keys (combined or otherwise) are applied to that mesh as an OBJ suitable to apply as a FBM.  I do it all the time.

Here's a sculpt I'm working on for Dawn 2, in Blender.  It's a shape key on the original Dawn 2 OBJ in a stack with a bunch of other "morphs".  I export that object in OBJ form with whatever morph(s) I want, and it just loads as a FBM.

The panel I wrote looks like this:

It takes 2 meshes (to calculate the mapping between the original vert order and Poser's vert order).  Then there's the 2 working meshes.  They are the morphed meshes.  One is poser vert order, the other is original vert order.  "Cast unimesh" applies the shape of a morphed original mesh to a poser ordered mesh.  (Not typically useful, but I needed it for something).  "Make unimesh"  applies the poser vert ordered mesh shape to a copy of the original mesh.  If the mesh is chosen, it either makes its shape the same as the Poser mesh OR adds a shape key with those vert positions (super convenient).  If the shape isn't chosen, it copies the original then applies the Poser vert positions to the correct verts (as determined from the map it calculates from the first two meshes).

Here is Dawn 2, with multiple shape keys (ie: "morphs") some of which are selected, all at a value of 1 (doesn't have to be, the value is also a slider 0-1).  When I sculpt, whichever shape key is selected is where the vert values being affected.  This helps me tune morphs so they work well together.  I can apply multiples, but select which ONE I'm modifying when I sculpt.

When I want that (or those) morphs in Poser as a single morph, I export the Blender Object in OBJ format, then I can load that as a FBM.

I'm thinking about putting two script together.  One in Poser, one In blender.  In poser, you'd select all the morphs you want to export and it exports each as an OBJ into a single directory.  In Blender, it imports those OBJs as Shape keys on a single Object.

Maybe two more parts: import that directory as a bunch of FBMs in poser, and export those shape keys as a bunch of OBJs from Blender.

Then I could bring a figure into Blender, with all the morphs I like, tweak/tune those morphs, maybe adding some.  And setup that figure with all those morphs, back in Poser.

At this point, it's just some scripting.  The essentials already work :)

Dawn 2.  Just the character and muscle morphs (made in Blender).  One click each, applied as FBM in Poser.  10 minutes to make those shorts and top.  roughed in blender, using the "fit brush" in poser, back in blender for quad remesh, solidifying edges, import into Poser, one click setup applied Dawn 2 as Donor rig.  one button copied character and muscle morphs.  In Poser I only had to use the smooth brush at the joints as the WM from Dawn 2 will not produce the correct movement for leg and arm openings.

No correction morphs.  And she's not bent to her limits (and she works best with limits.  They are really well setup.)

This is a v4 pose with only a few degrees of correction in the legs.  LF hair.  No corrections beyond Y and Z.

Single HDRI.  Ground as shadow catcher.  One button click (Ken's script) with a couple of checkboxes.  Superfly (ie: CyclesX) on MBP M3max (128GB RAM) 40GPU cores.  Took under 2 minutes, for 1200x1200px.

I have found Dawn 2 to be the easiest figure to work with (in Poser) and sculpt in Blender and Poser.  Her rig bends very well.  Probably the second best I've seen, but with waaaaay less complexity.  Which is what makes her so easy to work with.

I can't answer how easy for DS.  But if DS can import a shaped OBJ as a morph, then, when sculpting in Blender, it should be as easy as Poser, which is literally 2 clicks: export Object as OBJ from blender, load FBM from file in Poser.