With adsl, I'd just discard the isp device and use a cheap modem-only device.
As I said docsis is often MAC address controlled, so if you can't get the admin password to unlock the devices (http://portforward.com has lots of isp configs/auth details) you could buy your own docsis modem/router that supports configurable MAC address and simply spoof the isp provided device.
For fibre based devices usually you just have a ONT with an Ethernet port, so no modem required just plug in your router.
If you can give more info on the specific last-mile tech you're dealing with, we can probably make some suggestions.
Fibre to the home. I think your ONT is my NTD. Box on my wall that I'm not really allowed to touch, then Ethernet straight to my router which handles PPPoE.
I've never seen/used this type of thing before, but then again I've never found my need for mobile data that massive that regular 3g/4g wasn't a reasonable option.
Maybe thats just me though. My Thai phone provider gives me global roaming with unlimited data capped at ฿300 a day (about $10 a day). The last time my wife and I came back to Australia together, we had pre-paid Telstra sims. The time after when I came alone for work, I didn't bother, as the roaming cost worked out better than Telstra's shitty pricing, and I still got to use their network.
As for an actual solution, I doubt there is one an ideal solution in this case. Honestly, I would want to need access to a lot of other people's Wifi before I signed up for this type of deal - how sure are you this doesn't give the other Telstra members carte-blanche access to your local network, and how sure are you a judge will accept "but your honour, that could have been anyone downloading those pictures, I have Telstra Air".
I haven't had access to the Thomson gateway device for long enough to see how the traffic is segregated. If I do end up changing to Telstra I'll have a look, although I'm not sure I'd be allowed to solder up the serial-out on their device ;)
$10/day is $300+ a month - I pay $50/month for 7GB of data on Telstra's 3G/4G networks. I haven't actually needed to use Telstra Air because the middle of the city has free wifi by iiNet/Internode (RIP).
> I haven't had access to the Thomson gateway device for long enough to see how the traffic is segregated
Given the generally atrocious default security of most home router vendors, I'd assume its equally terrible, and maybe you get a nice surprise.
> $10/day is $300+ a month - I pay $50/month for 7GB of data on Telstra's 3G/4G networks
As I said, I was using it when travelling from home (Thailand), so it was $10 a day (max, if i didn't use it or used less than the cap amount, no/less cost) for unlimited data (still using Telstra's network). The alternative was to use a prepaid telstra sim, which from memory at the time gave me maybe 4 gb of data for.. $59 or $69?
I wasn't suggesting its an option for you, just explaining that those "free wifi" things always seem like a shitty deal to me, compared to the cost of your own data service.
> I haven't actually needed to use Telstra Air because the middle of the city has free wifi by iiNet/Internode (RIP)
Which ones? Sometimes the configuration is confusing, but I haven't found one I can't disable yet (my Ariss/Moto SBG5580 doesn't have a simple 'bridge mode' toggle, I have to disable NAT/NAPT to put it into bridge mode).