you can dream, this is possible in reality too
i mean.. CF shouldn't be any problem!
and you can get 3G for your 2400U, but you need to use a mobile phone for that. you can have two phones, one dedicated to data transfer to your hpc, and the other for talking
i doubt there's a pcmcia gsm/gprs/3G card that will work with ce 2.0... so you'll need to put up with recharging more batteries
it is what you want anyway isn't it? a palm a hpc etc... for your long journeys