Let me correct you. The "thin" mode in Umbra has been disabled due to upgrade to PoSv3 ... It was not a priority and thus will be redesigned inline with PoSv3 in the coming months.
I have followed this discussion and wanted to add that one of your own @kewde stated when I spoke to him about the code, that the 'thin' mode in SDC was broken:
And I just told you the reason. When we upgraded to PoSv3 we decided that there was a much better way to have "thin mode" nodes inline with our future design plans and thus it will not be upgraded as part of PoSv3 but instead later.