intead of a work around that is going to cause cache misses and be slower why not try to figure out why the dalvik cache is causing issues occasionally.
Ok, having SYS on nand, an DATA on nand... Android can only write to 2 things, Data partition, and SD Card (in fat32 i think... dunno about other FS on sd card).
So, the Dalvik cache is either in Data, where we are having lots of corruption, mostly on reboot without unmount, either by crash, or normal reboot, or SD. Yet i doubt its on the SD, for obvious reasons.
So to tackle this problem we would first need to solve the /data problem.
problem is, i haven't found a way of unmounting data... not even forcing...
This reminds me of USB Flash drives, and Windows2000, which had its caching policy all screwed up (fast writing vs fast removal), so we would copy, explorer would give the ok message (all copied) and slowly in the background start writing data to the usb mass storage, problem is, we would remove before it could have ended. result? nothing copied... and fat32 was kind enough not to give many errors (or not detecte them, i don't think fat32 as a incorrectly unmounted flag like ntfs...)