A couple of things....
Running a separate ground as you suggest is against electrical code.
Two wire into GFCI works just fine, provided GFCI is fairly new. Older one required ground connection.
In fact, using GFCI in a way say is common workaround for older homes with two wire connection.
As long as you observe basic electrical safety, 2 prong outlets are perfectly fine for soldering irons and oscilloscopes. It's just that margin of safety is little lower. I used to be a tech in Japan in 80s. Back then, all plugs are two prongs.
By the way, I am a licensed electrician. (My license is from Japan and I do NOT practice it)