Hey Roger,
I found a thread from the E90 forum on those guys replacing their mirrors. Because the E84 X1 is based on the E90, it should be similar to our cars.
https://www.e90post.com/forums/showthread.php?t=681912
I also found a thread on cruise control retrofit. Seems to be a little complicated, but possible.
https://e84.xbimmers.com/forums/showthread.php?t=406480
IMO, this is quite a bit of work for features that aren't that huge. Stuff like head unit replacement and backup camera install can be easily, cheaply, and reliably DIY'ed, which is why so many people do it. For the projects you mentioned, you'll be spending at least $1000 USD and a dozen hours with no guarantee that they will ever work. Considering most newer X1's (and other cars) come standard with these features and more, I'd say it isn't worth it.