Hi guys. I've got 4.12 version working. Almost fully. PARAGON and UT4 are both working.
Now, why "almost fully". This version have many changes in file formats, some of them were made in a way which doesn't allow UModel detect, which "sub-version" of 4.12 is actually used. Let's say, we have for 4.12 (in chronological order)
1. changed package format
2. changed serialization of basic engine's object (affects EVERYTHING what is stored in packages)
3. changed texture streaming code, with possibility to save texture data inside .ubulk files (a kind of UE3's TFC) - this is used by PARAGON
4. changed skeletal mesh, added "Recompute tangents" field (useless for UModel, but breaks mesh serialization, so I must be aware of this field). This engine sub-version is detected with some tech which is new for UE4 (i.e. not present in UE3) and called "custom versions". And of course, cooked unversioned packages entirely dropped these "custom versions" too. So I'm detecting this version just with setting "game=ue4.12", like EVERYTHING ELSE in this list.
5. changed static mesh format, to support "high-precision normals" (this feature is declared in 4.12 changelist).
Ok, version #5 is available for those who uses "UE4.12 preview release". BUT at least two Epic's games uses different sub-versions of 4.12. UT4 uses #4, PARAGON - #3. They are not compatible between each other, but all are 4.12. So, I decided to wait with #5 in UModel, and I stopped with version #4. So, to launch UModel with UT4 files, you should simply specify UE4.12 for startup, and files will be loaded.
Now, about PARAGON. It uses even older, pre-prerelease version of 4.12. At least those files I have. To load them, you should use new command line option intended to "hack" loader, and allow UModel to load this content. The option is:
umodel -pkgver=504
After this, you will be able to open PARAGON meshes.