Hi David,
As you know I'm in the process of getting my basement cleaned out in order to build a new layout. My old layout was 5x14x9 and had an O36 loop.
There are many scale steamers other than switchers which look right at home going over O36 curves: 4-4-2s, 2-6-0s, 4-6-0s, etc. Both MTH and Lionel has made versions of several of these. Also, the Railking Imperial Camelbacks are scale as reported here on this forum.
Additionally, both manufacturers have made slightly larger scale steamers which at least to me, look fine on O36 curves - these include Pacifics and Mikados.
Some of these older models can be had at a fraction of their original cost.
Another option is most of the Railking Imperial steamers. Several are within an inch to being scale lengthwise and width and height is frequently no more than 1/4 inch less. Before I went over completely to the 'dark side' of the scale world, I exclusively ran these steamers pulling 40' scale rolling stock and at least to me, looked just fine. I didn't have any of the larger articulateds, but most will look just fine from this line.
I hope this helps and look forward to seeing your progress!
-Greg
