There are no disadvantages whatsoever. Per your points:
1. Incorrect. You continue to use Stop orders, however, when the time comes that you calculated a stop trigger price that is already beyond the current close, you switch to a market order. In other words, at that instant, instead of placing another stop order, you use a market order instead. The previous stop order is canceled, and "replaced" by a market order.
2. You can use the stop order for the same bar exit without a problem. It would be senseless to enter the position if you already know that the price is beyond your RiskStopLevel, so in that case, don't even enter the position.
... well, if you enter a position with a market order, I guess it is
possible that by the time the order is executed, price has already moved past your stop trigger price. It's going to be a function of volatility and how tight you place the stop.
3. This doesn't have anything to do with the discussion of the market order. If you already have entered a stop order, it will continue to work after your power goes out. (Incidentally, a trading system should have a backup UPS so that would never happen anyway.)
I'm thinking you missed my point entirely. You should continue to use stop orders if you want to use them. However, you should add a little code to check (assuming long position):
CODE:
Please log in to see this code.
The result of this code should have little to no effect on backtesting your strategy, but it should minimize those order errors when trading live.