The Nusach is from the Rambam סדר תפילות כל השנה - נסח הקדיש where he says:
עשֶֹׁה שָׁלוֹם בִּמְרוֹמָיו הוּא בְרַחֲמָיו יַעֲשֶׂה שָׁלוֹם עָלֵינוּ וְעַל כָּל יִשְׂרָאֵל אָמֵן.
The Behr Siddur, pg. 131 (Siddur Avodath Yiroel, without footnotes from Yitzchok ben Aryeh Yosef Dov, printed by Rodelheim, 1868) it says:
"It's from the Rambam and in all Sefradi versions, also in Nussach Roma. But the Ashkenazim do not have this version, except in the Kaddish said by mourners during the 7 days of Shiva.
In the old brown Sidur haGro (אשי ישראל p. 290) the end of Kadish DeRabonon has the nussach:
עשֶֹׁה שָׁלוֹם בִּמְרוֹמָיו הוּא יַעֲשֶׂה בְרַחֲמָיו שָׁלוֹם עָלֵינוּ וְעַל כָּל יִשְׂרָאֵל ואימרו אָמֵן.
No explanation given for the change from pg. 182 where he has the standard Ashkenaz version.
The Yerushalmim claim to have a Mesora that for the Kadish deRabonon one uses the Rambam's Nussach, but I have never seen this written anywhere. That may explain the ArtScrolls' version.