well, the first thing i noticed is the comment about water: where did you do your research on that?
according to dr william sears in his "the baby book" he says that babies who are fed formula NEED a bottle of water every day - the concentration of formula is way higher than that of breastmilk, and although this may sound like a good thing, it actually causes constipation among other misc digestion problems.
remember constipation isnt necessarily the abscence of stool, but difficulty passing stool... or extremely hard stool. everyone, adults included, should have stool that is moist and soft - almost like what most adults consider the runs... except not watery. it should almost always appear wet. anything else is a constipation issue.
the key is fiber...if your child is on solid foods you could certainly add milled flax to the cereal. baby wont care, and it will help baby poo!
OTHERWISE, back to your question, as long as you arent leaving the bottle in the crib with baby (causing ear infections along with tooth decay) there is nothing wrong with falling asleep while drinking. theres nothing wrong with it unless the bottle continues to sit in baby's mouth ... you know? im sure that it will be just fine.
do you use a nuk? that might help, giving that instead of a bottle.. babies NEED to suck. an unfulfilled need turns into an undesireable habit later. EX: a baby in my day care was not allowed a nuk, and so he grinds his teeth. all day. every day. its so annoying and painful for me ....
but thumb sucking is among another habit of not allowing a nuk.... however, again, its your choice. obviously, there are problems with extended nuk use too. my son is 20 months and only uses it at nap and bed time... and usually has it spit out an hour after falling asleep. i just bought the last set of nuks yesterday... im not buying more after this. im sure just like breastfeeding, he will wean himself when hes ready. but i do have limits. :D