Spark Gaps the hard workers. The best materials.

[Jeg]

The problem starts when you need hv and high current together. I have tried in the past cascading mosfets but over some 2000v I had some problems like explosions

I really hate spark gaps. What about this gas discharge tubes of Don's? I think i have to reconsider the more mosfets solution.   
On the other hand, spark gap is raw power. You can feel it to your bone!

Thanks
Neo-x

[Neo-X]

@JEG

Try IGBT i know it can handle high voltage, high current and it has fast switching speed. You can use the second picture for teslacoil circuit and replace the transistor with IGBT

[Jeg]

Igbt is partially a good solution but again it is not as when a gap is firing! By the way, both of your attached images have mistakes.  But as an idea is fine and very common in SSTCs. Thanks