I completly understand what you are going throuhg, my daughter, who is now almost 8 months, has had oatmeal in her bottles since she was around 9 weeks old, due to pretty painful acid reflux. We use born free bottles and for us, the y cut nipple flowed too fast for her but has done well with the variable flow nipple, which avent offers as well. that way, you can adjust the flow as your baby eats and grows. She still gets oatmeal in her bottle, just less of it and she still uses the variable flow nipple.
I know for me, it was so difficult for me to get her to drink her bottles that i didnt' want half of it to pour out her mouth.
As for my opinion about putting rice cereal or oatmeal in bottles, if it makes it less painful for your baby, than do it!! my daughter has no allergies from eating oatmeal from an early age, and we didn't start her on any other solids till she was 6 months and she does great with them.