Mikuo Hatsunes way of getting Dorothea on an MMS
1stly , Stuff I used ( you don't need all of it really )
A - Pliers and Wire Cutters (not needed so much)
B - Powered Hand Drill and a 5/32 Drill Bit OR equivalent drill bit thats the same thickness as the Shinki Sprue connectors ( [big] IMPORTANT[/big] )
C - The Shinki connector sprues ( need a long piece for the head )
D - A 'sharp' scalpel knife/hobby knife and some Files (the knifes needed the most)
E - Spare bodies to put her Dorotheas head on ( MMS3rd Naked Ver4 Skin Tone suits her most )
F - Kos Mos to laugh at you incase you hurt yourself ( not needed )
alright finely cut Dorotheas head off with the Scalpel knife ABOVE the Choker
then with your drill , drill in the middle around 3mm
now onto the head
you're going to have to cut off all that plastic from the rest of her neck which is moulded on to the bottom of the head , might need to use the wire cutters and pliers to cut and pull away the plastic , however its probably better to cut bit by bit away with the hobby knife

Red line shows the area your going to cut within and sort of crater it cause you also have to take into consideration the neck piece of the shinki to have room to move around in
light blue line is the parts of hairpiece I had to cut off to make the fitting on more better as it sort of collides into the left side of the MMS back
as I've mentioned you need to crater it sort of like how most Shinki heads are so it looks sort of natural to put on , after you feel like you've got a nice crater and it looks alright , drill into her head around 7mm , then cut off 1cm from the Shinki connector sprue and use the files to thin it down as theyre abit thick for MMS 3rd necks
if you're fine with the measurements on BOTH Dorotheas Body and the MMS body you're using , glue the end of sprue you're going to shove into Dorotheas head and wait for it to dry ,
and then you can have Dorotheas head on an MMS and any Shinki head on Dorotheas body
since Dorotheas Hair piece is like Altlene , its pretty much impossible to put her with armour which requires the back piece
anyway , enjoy , I'll answer further questions and might improve the instructions , I do plan on buying another Dorothea (after trying her with a Murmeltier body) so I might do the tutorial again from scratch