Here are the third party skinning products I found so far:
TMS Skin Factory. This has been discontinued.
VCL Styles Utils. This extends VCL Styles and the issues with 10.2 Tokyo remain.
VCLSkin. This has not been updated since XE6.
Almediadev. Just like with DevExpress, we would need to replace all the standard controls with their specific versions in order to apply their skins.
I will update my answer as I find more.
Unfortunately, any answer where we have to replace the components offered by Vcl.StdCtrls or Vcl.ComCtrls with versions specific to the third party package is not going to work. We have 2500 TButtons alone across all the programs in the suite.
EDIT: In the end, we found an answer, or workaround, to the System Exception problem that had us looking at alternatives to VCL Styles in the first place:
我来说两句