It's pretty spotty, but I did find a BVH called "AudioMotion Male Bind" which is just a T-pose. It would probably work OK for other BVH files... from AudioMotion... I found it here.

I think you're right that you'd need a different T-pose for each supplier.

But I didn't use a T-pose for any of my experiments. I followed Will's workflow in general, but I just started right from the "drunk" or "female walk" BVHs. It seemed to work OK, although I had to pre-pose the model before applying the constraints in some, but not all, cases.

A:M's handling of actions on different characters works really well as long as the rigs are similar in the way the bones are, in relation to the geometry and their parent bones, and if they are named the same. For example if you have two characters; one with its arms modeled straight out, and one with its arms modeled down at a 45deg angle from its torso. The motion for the bicep bone made on character (A) will work on character ( B ) as long as: both bones are named the same; the roll handles of both bones exit the the same part of the arm (for example the back); the bone aims the same way in relation to the geometry; and the parents of the two bones are oriented the same way in relation to the torso. When an action made for character (A) works on character ( B ) those two characters are said to have the same rig.

Sometimes you end up with a really cool action you would like to use on a character that has a rig other than the one the action was made with. To use this action you can use similar steps that you would to use a bvh action on your character. That is you would load the action on character (A) in a choreography, and then add character ( B ) to that choreography (both characters at the origin) and constrain each of the rigs control bones to the bones of character (A). When character ( B ) follows character (A)'s action as you like, right click on character ( B ) and choose "Bake All Actions" from its context menu. Then right click on its choreography action and choose "Export as Action".While this is labor intensive if you save this choreography before you bake, you can reuse these constraints to make other actions for character ( B ) from character (A) actions.

See William Sutton's Mocap Tutorial for some constraint methods that are useful for this process.

This would be a good process for someone to write a step by step tutorial on.

Thanks, zachBG for link with T-pose.
For example rig_bvh - all bones named as bvh-bones.
All constraintes Orient Like, only hips also Translate To.
Come in handy..
Thanks serg2 for ideas.
Sorry for English - better pictures and projects.

I'm so sorry ... I just had to do this

I think this might do it...

Create an additional Choreography Action and rename it "MuteAction"

On Frame 00:00 do a whole model keyframe with the Shift Key and select "In all filtered key channels".

This MuteAction should be set to "replace" and dragged to the top of the actions in that Chor. It's redbar should already extend the length of your Chor. Don't make any other keyframes in "MuteAction". It will now be overridden by any other action you create below it. Since it merely keyframes the inital default state of your model, it adds no animation by itself.

However, you can temporarily drag any or all of those actions above the "muteAction" and they will be cancelled out by its single keyframe at the beginning of the timeline.

You would need to remember where you dragged your actions from.

But this would fail if you were animating the blend percentage--also, you can't keyframe the blend percent with the Replace method.

Robert's suggestion sounds very interesting and really cool if it works... hmm...

Sounds like a good feature suggestion for http://www.hash.com/reports

Done. Thanks for the encouragement.