from personal experience and im not a developer, ill say its difficult to jump so fast because something will break. it needs intensive testing before moving to a new version. not like anyone can just copy and paste the codes over. this is my opinion anyway.
Eh... No not at all. Its init.d script so its run after new version install. Of course this can also be done via cron more often. I think Wajk has same method in his rom but I'm not sure if he has it working properly.
I know this an older topic, but I still wanted to reply on the fstrim thingy. Why don't you use the WIUI ROM? It has a lot of extra features, like fstrim and battery tweaks and it looks like a normal MIUI ROM (which is the main reason I choose it).
I would love to see at least 4.3 and it's advanced rights management. If we refere to the update stages that htc had published here www.htc.com/us/go/htc-software-updates/ where are xiaomi devices (assuming that the stages are the same)?