failover via comcast tunnel?

I'm looking at some sort of 50-100mbps failover link in case my
primary is down.

My options seem limited particularly since I'm cheap.

I see Comcast has unlimited data business links in this range but I'm
not sure I'd want to deal with the management issue of BGP or swapping
ip blocks etc with them in an emergency. I just tried calling their
business sales line and after the initial "Thank you for calling
Comcast Business Services etc" it dropped me...three times. Yeah, that
builds confidence.

So I'm thinking something more like using their service as a raw
bandwidth pipe and tunneling to an actual route provider?

Crazy? Anyone done anything like this? Are there tools for that?
Other, similar suggestions?

Feel free contact me off-list.

You could tunnel to a data center.

Or NAT out their service.

Tunneling via EoIP would allow you to stay within their ToS.

FWIW we do expect to pay for this service, by "cheap" I just meant,
well, cheap, but not free. It's all relative I suppose.

But thanks for the response thus far!