WIP: converted ie15 into a device and made two interfaces for it -- a rs232 slot device, and a standalone driver. Next step -- overlay video output from 'kgd' on top of 'ie15', just as in real life.

Code
./mess ms1201 -rs232 ie15 -rs232:ie15:rs232 "" -ld

Driver ms1201 (MS 1201.02):
   <root>                         MS 1201.02
     bankdev0                     Address Map Bank
     dl11                         DL11 @ 4.60 MHz
     kgd                          DVK KGD
       gfxdecode                  gfxdecode
       palette                    palette
       scantimer                  Timer
       screen                     Video Screen @ 15.40 MHz
     maincpu                      K1801VM2 @ 4.00 MHz
     pc11                         PC11
     pclk                         Timer
     rs232                        RS232 Port
       ie15                       IE15 Terminal
         beeper                   Beep @ 2.40 kHz
         gfxdecode                gfxdecode
         keyboard                 15WWW-97-006 Keyboard
         maincpu                  ie15 CPU @ 3.08 MHz
         mono                     Speaker
         palette                  palette
         rs232                    RS232 Port
         scantimer                Timer
         screen                   Video Screen @ 15.40 MHz
     vhd                          Virtual Hard Disk