3G Wireless Router/3G USB Modem Interoperability

I want to buy a 3G Wireless-n Router to fullfill the same job that DSL Routers did with DSL modems on fixed telephone lines: i.e. share the internet connection between more than one WiFi device

Grateful if anyone can help directly, or if outside scope of this forum, point me to some sites more likely to address the issues.

Last time I installed a DSL router on PSTN, from memory, the browser accessed 'Management Console' had a very comprehensive 'ISP Setup' page, that allowed the user to program ALL necessary variables that are a function of the ISP, PPPoE, User Name, Password etc. I got the impression such a Router could be taken to ANY Country/ISP, and was GUARANTEED TO WORK because the ISP setup page had sufficient variables for all countries/ISPs

With 3G Routers it appears the above ISP/Modem Setup is less well defined, and unlike with DSL routers, 3G Routers all appear to require ongoing support from the manufacturer in the form of 'firmware Updates' to support changing ISP/3G Modem standards, which leave the customer highly dependant on the manufacturer to keep supporting the product with continuous ISP/3G Modem updates. - not very satisfactory from customers point of view. Is this true, and why ?

I realize most, if not all 3G USB Modems, tend to be rebadged by the 'Carriers', are 'locked' to them to hinder you switching 'carriers', and are pre-programmed with their 'Connection Manager' which on 1st use, is auto-installed into the client PC. But I don't see why that should prevent 3G modems from working interoperably with 3G Routers.

All 3G Router specs I have seen, seem to have a LIST of 3G Network/modem models, their product will work with, implying unless your ISP/Modem combination is on the LIST - it will not work. Emailed Netgear on this. They gave no explanation, simply saying unless your combination was on their LIST, it DEFINITELEY WON'T WORK. Another maker said over the phone, it is ONLY MODEM COMPATIBILITY that matters, not the ISP

So grateful for clarification if it is truly just the 3G Modem that needs to be checked for interoperability with a 3G Router, or the ISP/Modem combination, and also if someone can list the parameter values I need to acquire from the ISP, and also the Modem, to allow the 3G Router maker to assess interoperability, or update their firmware to make so.

I gather the ISP's are reluctant to publish that information because it makes it too easy for customers to choose their own Router and how many pc's or other devices they hang off the Wifi connection.

Does anyone know of a utility (pref. freeware) that can read the necessary parameter values from a 3G USB Modem ?
I notice at least one ISP seems to rely on a PIN to authenticate the user, not the 'User name' or 'Password.

I travel frequently between countries, so not viable to enter into the typical 12 or 18 month ISP 'lockin' contracts. I usually stay where the owner of where I stay already has a ISP contract, and share use of the connection between 2 pc's - easy enough with DSL as mentioned above. Reason I want a Wireless-n Router is convenience of not running wires, and HD video streaming to the TV (802.11g too slow)

The ISPs I connect to are always 3G HSDPA/UMTS. Grateful for any enlightenment on the issues.