Same here Babyboos - ReadyBrek is the easiest to make up, since you can use hot water then thin it out and cool it down with milk, no need for cooking or microwaving as with real porridge oats.
Don't use the new Oat-so-Easy Instant Porridge as it's full of sugar and flavourings!
For my babies and pregnant mums, I add a few teaspoons of Lactol powdered kitten/puppy milk (or you can also use SMA or similar human baby milk powder - soy version if you like) to the dry Readybrek, mix well then add hot water from the kettle. Then thin it out with a bit of cold water, and it's usually cool enough for them to have straight away. Instant creamy lovely hamster porridge with no messy washing up to do! I've been known to polish off the leftovers myself!! (Although, let me say, not if I use Lactol - then the rats get to finish it).
And yes, the grown-up hammies get a little bit now & again when I'm feeling generous or if they beg convincingly enough
I like your idea of adding bits to it - not tried that yet. I guess hemp seed and linseed, possibly some bird seed like millet, some scrambled egg and maybe a pinch of seaweed powder would be a nice addition.
*goes off to plan porridge menus*
PS: for our American friends - what we call porridge is what you call oatmeal