All platforms have their own trade-offs. I think Zorro has a pretty good value-to-cost ratio.

A combo order is nothing more than a series of orders placed simultaneously. There may or may not be cost savings with a combo, and this depends on which broker you are using. You can make a virtually identical system with or without combos.

You would need lots of volume for the difference to be non-negligible. Why would this of all things be a deal-breaker?

Like I said, if you want a feature for your plugin of choice, ask for it.

If you have written at least one Zorro script, you are officially a programmer. Congratulations!