You can do the reopen on any device as many times as you want. You would do this, for example, to start a program on /dev/con1, then start the shell on /dev/con2, and then start another program on /dev/con1 again:
[+script] .script = {
...
reopen /dev/con1
prog1 &
reopen /dev/con2
[+session] esh &
reopen /dev/con1
prog2 &
...