SSH through firewall

["Ginsberg Rainer (QI/INF4) *" <Rainer.Ginsberg () de bosch com>]

Hello,

I'm thinking about allowing users in the trusted network to do ssh through a

non-transparent application gateway firewall into an untrusted network.

Do you think this is "secure"? I'm not sure because users can tunnel all
kinds 
of protocols in ssh. What would be possible attacks?

Do you think this is feasible with a non-transparent firewall? Do you know 
a firewall that is capable of this?

Thanks for your thoughts,

Rainer