Yes at that price point, I would be expecting a plug and play solution. If a grip was available to integrate with a custom built flight stick then that would be a good option as well. Not so sure on a good price point for that...
Horses for courses - some people like to custom build and would prefer just a grip and then others would prefer the whole thing in a nice and easy user friendly package.
Up to you chap but I would say go ahead and do the grip first, followed by a collective - just my two pence worth though