Do a STEM major for OPT extension?

I'm an international student majoring in finance at a target who wants to work in IB in the near future and I'm already worried about losing the H1B lottery. I don't wanna get kicked out after ~9 months of work so I'm thinking of switching to/picking up a double major in math for the STEM OPT extension (but I'm worried my GPA might take a hit). Has anyone here been in a similar situation? What do you guys think?

P.S. my citizenship is totally useless (non-EU/Chinese) so transferring to London/HK might not be a possibility either but I may be wrong so please correct me.