I am very strongly of the view that we should preserve the crown's prerogative to deploy the military without necessarily having the approval of the House of Commons.
That being said, there is the question of what role the House of Commons does have in debating these missions and obliging the government to, at the very least, outline what it intends to do, what it intends to spend. And if it needs incremental funding from the House it should be able to secure that.
Again, the reason I'm so adamant about this is that to my mind, accountability in our system is preserved when the executive is fully responsible for the decisions it makes and doesn't have the capacity to launder its decisions through the House, as I believe this government has done on a number of occasions. I find that really muddies accountability for national defence.
That being said, there should still be a debate in the House, motions in the House, where members of Parliament have the opportunity to debate these missions. That should be required. The government should also be required to divulge the full information in terms of costs, in terms of what it's deploying and what it foresees as the end game.
Similarly, on your second point, there should be a parliamentary committee with security clearance that's able to look at operational secrets and operational details so that members of Parliament have a much better sense of exactly what is happening on the ground and whether the mission is operating as successfully as what they're being told.