After nearly 50 years in the electronics industry, I can tell you that in the engineering profession one DOES NOT 'Mess with Mains AC".... Without an isolation barrier and a very good one at that.
Should you just destroy the equipment under test would be your lucky day, the more conservative the design the better. Assuming that this device is for your own use... It is Still Most Dangerous
and Not for the general public. One more thought... In the US we have various safety organizations that would prohibit the sales of that device as unsafe and Europe is a great deal more strict
Docedison