I don't think liquidity will decrease so much that sl-m orders will be risky .
Already not all stock options are liquid enough for high volume Market Order.
For the index futures market order will execute as before but with less volume obviously, the cost of impact will be much more for volume traders. Actual breakeven will be much higher due to slippage.
The broker will try to block market order on stock specific options.
Why it is dangerous to trade with stock specific F&O where liquidity will dry out??
Bcoz u will see sudden volatility spike which will take your stop losses frequently. Trailing stop losses will be hit frequently also. Overall trading will be more difficult in reality.
30-50% margin increase mean volume will certainly drop for stock specific f&o.