Such an extraordinary initial margin is not a regulatory requirement and it is not SPAN. IB is discouraging you from trading of options with far (September 2017+) expiration. The liquidity is not great.
We did not cut futures trading in retirement accounts. We increased overnight margin. The point was not to protect IRA customers but rather protect IB. We lost huge money in 2015 on Swiss Frank debacle. These losses were unrecoverable for IRA accounts.
This "one can work on Chinese exchanges next on only USA exchanges" is not correct. If you are HK resident you are covered by IB-HK and you can trade everywhere in the World.
You cannot define IB as an American broker. Check the bottom of https://www.interactivebrokers.com/en/index.php?f=564. Interactive Brokers Hong Kong Limited is a Hong Kong broker.
IB does not like to hold low liquid futures on your behalf. It is a way to tell you that. The initial margin for VIX is increasing steeply starting from June expiration. This additional initial margin charge was put in effect many years ago.
Brighton,
IB made Hard Red Winter Wheat available many months ago. It is easy to check futures availability here https://www.interactivebrokers.com/en/index.php?f=marginnew&p=fut
Did you try to call our Hong Kong office +852-2156-7907? They should be open from 8:00 HK time according to http://www.interactivebrokers.com/en/?f=customerService&ib_entity=llc.
It is a bit hard to explain in precise terms but roughly if you have just one or two stocks or ETF in your portfolio, it is concentrated. If you have let's say 6 or more about equally weighted stocks or ETF, the portfolio is not concentrated.
The margin is 30% if you are concentrated in this ETF. It is 15% otherwise. This information is valid for Interactive Brokers portfolio margin account. Other brokers could have very different requirements.