Load balancing based on throughput?

Greetings to all,

Since I am new here and for calibration, let me say that I am certainly not a network engineer, but did in fact work for a national cable modem ISP (Softnet Systems) and managed a fiber to the home trial system in Palo Alto around 2000 and set up an early pre-Wimax wireless Internet distribution system in Oregon. So, I am generally familiar at a management level, but have a farily large experience gap.

Living now in the mountains of Panama, we have a cable operator and DSL from the phone company, along with various privateers mostly poking Nanastations into the hills. 

The cable operator has under-provisioned his nodes, leading to frequent saturation and bendwidth falling to around 100k when the most people are streaming Game of Trumps, or whatever, leading to widespread disgust with the cable company. The DSL is only 3mbps, but rock solid dedicated bandwidth. I use both.

So here is the question - is there a way to monitor the throughput of the cable WAN and when it drops way below the throughput of the DSL, simply cut it off until it comes back? Is there already a way to do this that I am just unaware of? Finally, with the EdgeRouter, it seems that the tools may be at hand to solve this problem.

The reason for doing this is what I have observed over a couple of years of frustration using TP-Link dual WAN routers, and maybe I am totally wrong, but - Round-robin works great at about 2:1 cableSL when both WANS are working good. But with a round-robin scheme, when the cable WAN hits the skids, it drags everything down with it. It never dies entirely, just makes the whole system really slow. 

So an approach would be - and here is where I need help  - to generate a kind of "download-ping" which would download 1-10k or so bytes every x seconds only on the cable WAN. If the latency to end of download indicated low thoroughput, do it again. A few low readings and then start testing rapidly to build a statistical picture for say, ten seconds. Then change the weighting to 0:100, but keep testing the cable WAN until it recovers.

There are lots of people out there who are really ticked off at their cable operators. DSL is cheap and reliable, but I am hesitant to suggest a dual WAN approach because the existing load balancing methods don't work well with the low-throughput failure mode. 

Any ideas and suggestions would be most welcome. Give me a pile of ERLs with this script in them, and I"ll show you  a pile of ERLs that would be installed by next Monday. Maybe others reading this could profit as well. 

Thanks in advance,

Mark