Add new stacking method

That is stack mode blending. Its a Adobe Photoshop feature that blends a smart object that is a stack of images.  If you are a Programmer and have developed an other method download Adobe SDK. You may be able code it as a Photoshop Plugin the could blend a smart object that is an image stack using some other way if you want good performance.

For if you opened the layer smart object into Photoshop and used Photoshop feature and tools to blend the image layers and save  the results to update the smart object layer rendered pixels with a Photoshop Action or Script the performance would not be good if it can be done with an Action or Script.

I know nothing about LR I do not use it. It does not support layers I know but can pass a list of image to Photoshop that Photoshop can stack..

Bridge pass list of file to Photoshop via Bridge talk scripting.  Again for good Performance it would need to be a compiled Photoshop Plugin.

Photoshop Stack Mode Blending is fast it not done via a script.  The Layers object is a stack of image layer the plug-in would need to blend that stack and replace the pixels Photoshop had rendered  for the smart object layer.

What do you mean be new stacking method?  Adobe supplies a script Load Files into stack the has alignment option that can align bracketed images and stitch panoramas.  There is also Adobe  Photomerge script the uses other Adobe Scripts like StackingSupport found in folder Stack Scripts Only.

A script should be able to stack layers any way it wants to.