The dogs you are describing are not hybrids - a hybrid is a cross between two different species, so a mule is a cross between a donkey and a horse (isn't it?) "hybrid" dogs are just cross breeds with a fancy name and even fancier price tag! 
Don't be fooled by size, a little dog often needs as much, if not more exercise than their bigger counterparts and can often be scattier. .
Spaniels are lovely dogs - but again, need lots of exercise and stimulation as they are bright. I think a cocker spaniel is more of a house dog than a springer, unless you are going to do somthing "with" your dog then a springer might be a bit much.
TBH it is really difficult because everyone will come on and recommend their favourite breed. Me personally, my next dog is likely to be another rotweiller although my DD is 8 now and I have two young JRTs so the next dog wont be for many years yet :( Rotties are great, don't need too much exercise, generally lazy arses but happy to go for a long walk, solid calm temprements (yes, really!) and not likely to be bouncing off the walls, mine were happy to be left. They are not for everyone of course, but mine were easy to train, i had one from a pup and one as a rescue with issues.
If i can say only one thing to you its this - please please please consider a rescue dog. There are so many dogs out there that need good homes and you sound like you are doing your homework and have thought it through so would be just that. Our latest rescue is a JRTx that we got from the dogs trust, he was about 6m old and they happily homed him wiht us and our DD who was 7 at the time. He is the apple of my eye (i know you shouldnt have favourites but....) he is so funny and sensitive, he "talks" to us all the time - so will growl if he wants to go out for wee, a different growl for his dinner and a lovely little worried growl if i am upset and he just wants to say, "whats up mum". Best thing - no toilet training 