Please give option to transfer weights from a posed mesh without doubling up deforms

As it stands right now, if you have a posed character that is anything other than the rest pose, transferring weights from one that mesh to another in weight paint mode (or using parent deform with automatic weights) it essentially “doubles” up the deform once you set up armature and fails to be accurate at all.
Sometimes using a deliberate pose to design/make clothes is easier than the rest pose. If you have animations then changing rest pose of the source mesh is disastrous.
Why isn’t there an easy way to transfer weights from a posed character mesh? I know why this happens, it’s just strange that it’s never been addressed.

Same boat after designing an piece of clothing on a T-pose.

However weight paint transfer works just fine.
there is a workaround for getting back to a regular pose, since that’s what needs to be imported and used by most engine.

First, duplicate the armature. You’ll need the original rest pose in a minute, so make sure you have a copy.
Second, Select the armature (copy or original) that is Posed in the T/other non rest pose, go into Pose Mode and Ctrl A apply pose as rest pose.
You now have a perfectly useless armor, but the pose matches the clothing you made.
Enable the armature you copied, and clear/reset the pose.
Now in pose mode on the armature you modified, move the bones that need moving to match up to the original pose. You can use the second armor as the “end” point for near perfect accuracy.
Having now posed the T pose to be the original rest pose, Apply the armature deform. Get rid of the modified armature. Parent to the copy or the original non modified rest pose armor, and apply the armor modifier.
All done. Except you’ll also have to fix other stuff if the clothing was wider then the base mesh like mine.