I have never tried this but I do know that the internal diodes (there are usually more than one) are part of the secondary
high voltage design. If you could magically vanish the diodes the resulting geometry would not work like a coil that
was designed for AC only.
Your best shot at getting an AC flyback that is worth a damn is to find vintage Thordarsen flybacks in the FLY3XX range.
Someone in China makes a decent AC flyback because Information Unlimited used to sell them. But I've never found one.
My last try was an AliExpress unit that died way before it reached the claimed voltage.
Cheers.