Sarbanes, I'm going to second the suggestion of Air Canada Aeroplan made earlier.

Your approximate travel seems to work out at about 90k miles per year. (Note that I am basing this on 3 returns per year from the mid-west as a mid point to London (Europe) and 1 each to Tokyo and Singapore as well as 7 return transcons per year accounting for the fact that you won't be doing transcons every time). You may in fact be travelling a bit more or less than this but you will still be travelling at least 35k BIS miles per year.

Based on this you will easily make the requirements for AC Elite and if you are willing to play around with routings and possibly pay a little bit more for your trips you may even be able to get up to 100k miles and AC Top Tier Super Elite.

As an AC Elite you will be able to access business class lounges when flying on *A carriers (Note: this is not available to you in the domestic USA if you have status with UA or US). You will also be able to select upgrade certificates for use on AC flights. In these cases you would have to fly to your destination via either YYZ, YUL or YVR as indicated above.

It is worth noting that earning with AC may not in fact cost all that much more than simply choosing the cheapest each time. Admitedly you may pay more for your domestic flights as you won't be able to fly Southwest and collect rather you will have to fly UA or US if you want to earn. This is partially offset however by the fact that AC often has cheap fares from the USA to Europe and Asia via Canada which make it worthwhile to fly AC on these routes.

Overall, even if you choose to fly other airlines some of the time, your travel patterns indicate that you can easily make AC Elite, gaining the benefits of *G based on your travel pattern. Further, I can see that you will benefit from the lounge access as well as upgrades using certificates on AC which will come in handy on flights such as USA-YVR-ASIA. I hope all this helps.