The whole point of a "tweener" is to move data *between* truly vintage (such as PC/XT/AT or older) systems and lobotomized modern systems.
You would have a rather hard time these days finding a system that can run Windows 10 well and having even the minimum to act as a "tweener". It would need at minimum a real FDC and support for 1.2mb/720k/360k drives.
And then any NT based OS (NT/2000/XP/Vista/7/8/10) has rather poor floppy support.
In my opinion, an ideal tweener would:
-Have any Pentium, K6, or Athlon era CPU
-Have a generic AT or ATX case
-Have BIOS support for *two* real, internal floppy drives.
-Have Ethernet Networking (easy to add)
-Have Windows 95 OSR2 or 98SE as the primary OS for easy DOS access (ME/2000/XP are more difficult)
-Have USB ports for flash drives.
-Have at least one ISA slot and plenty of additional slots (AGP/PCI)
-Ideally the FDC should support FM encoding, but that is rather uncommon and hard to tell just by looking.
-The motherboard should use a coin cell CMOS battery instead of a Dallas or Odin integrated clock/battery chip.
There was a previous thread about tweeners here:
http://www.vcfed.org/forum/showthread.php?50935-PC-quot-Tweeners-quot
And a test of some of the last motherboards with FDCs here:
http://www.vcfed.org/forum/showthread.php?39615-Recent-motherboard-FDC-and-quot-legacy-quot-tests
If you require a "modern" computer that interfaces directly with floppy disks, then you should look in to adding a Kryoflux or SuperCard pro.