First off, the partitioning. Google people have repeatedly made mention of the OTA updates needing to be kept internal in the /cache partition for reliability purposes. This is a load of horse crap;

- check sdcard for required space.
- if sufficient space, disable the “unmount” option, reserve space, download update, install from sdcard.
- if not sufficient space, do nothing.

So we have 3 partitions that we can play with; /system, /cache, and /data. With the elimination of /cache, /system can be doubled. Lets not worry about /data at this point, leaving a HUGE amount of space for updates.

How to:
This is a multi-stage process;
1) backup /data partition to sdcard and install new SPL with new partitioning

##HAIRY SPOT HERE## — what do you do if the user removes sdcard at this point and maybe deletes everything from it? DUH! The SPL allows installation of signed system images from sdcard. If they do something stupid, give them the link to the update.zip and tell them to put it on the sdcard.

2) reboot
3) new SPL begins update from sdcard
4) restore backed-up /data partition to same-size /data partition on device.

*nothing has changed in the overall system except that /system is doubled.

OPTION #2:
Forget about the /cache partition altogether. Don’t bother repartitioning, just reassign the purpose. Mount the filesystem at /system/app instead of /cache and make /cache a link to /data/cache. DONE.

Apps-to-sd:
Seems to me that google is quite resistant to this. They don’t just fail to do anything, they actively come out and say that it can’t be done. B.S. There are three directories where installed app data exists; /data/app, /data/data, /data/dalvik-cache. Let the launching mechanisms also read /sdcard/apps/app, /sdcard/apps/data, /sdcard/apps/dalvik-cache. User account for each app should be stored in an encrypted database within the sdcard and should be a specific range of userids that can never conflict with the internal userids. You are guaranteed that app and userid integrity is maintained by the user database encryption, you are guaranteed no conflict by restricted userid ranges. Yes there are other issues, but come-on — ask me and I’ll answer them ALL.