Karen Gillan, the actress playing Nebula in the MCU has recently shown interest in working for the DCEU as well, wanting to play the role of the notorious Joker.
During a recent Q&A session at the Florida SuperCon, she was asked if she wanted to play the role of any character in any other fandom and Karen displayed a strong interest in playing the role of a female Joker. A female Joker appears in the comics in one of the most iconic storylines called Flashpoint. With the next solo Flash movie believed to follow that storyline, Karen Gillan might have her wish fulfilled should the studio want it (If that happens she would be a part of MCU, DCEU, and Doctor Who. The geek is strong in this one).
Karen Gillan might not get the role however, as the part of Martha Wayne is already played by Lauren Cohan in the DCEU.