If it's a cheap phone, I'd rather them do something brute force but reliable than try and be clever when they know they don't have the budget to QA it.
I honestly consider that a pretty reasonable trade-off.
I honestly consider that a pretty reasonable trade-off.
It is a complete image, but phones today have nontrivial state that may be a problem - e.g. your baseband processor might have its own rom with its own update protocol, which changed between image 2 and image 7, so image 10 after image 1 will be unable to update the baseband.