[sdiy] midi optocoupler isolation voltage?

[Christian.Bergmiller at daimlerchrysler.com]

Hello,

I have two Questions :

I already designed some applications that use optocouplers to receive midi 
messages. (and uC's to decode them of course...)
Since Optocouplers are rated for max. Isolation Voltage - Are there any tried 
and trusted methodes to
limit the voltage difference between the midi devices? (varistors, spark 
gaps,neons...?)
I just wonder if electrostatic charge could be a problem since some midi 
devices are completely ungrounded (battery opperation etc...).

Second Question :

I try to design a midi to relay interface (a bit of "to reinvent the wheel" 
..but i love to invent, so its fun)
I want to build the output stages with N-Channel PowerMosfets driven direcly by 
CMOS ICs.
Problem is i never done this bevore....
So far i only plan on the common EMF suppression (?) backward diode parallel to 
the output (solenoid/relay...)
any further tips that would increase reliability and/or electrostatic charge 
withstand ?

thanks in advance

Christian