One food for multiple cats with special needs

I have five (heaven help me) cats, three of which have special dietary needs.
   
1. Ned needs low ph diet to prevent crystals from forming in his bladder.
   
2. Bob, the kitten, needs a food that is easy on his stomach to prevent loose stools.
   
3. Gracie is fat and needs a food that isn't particularly high in calories.
   
4. Andy and Izzy need a basic, good-for-them food.
   
I have to free-feed them to accommodate our schedules. Are there any foods you can recommend that would possibly work for all of them?

First: Are the cats indoor or outdoor? If they're indoor, this would simplify things, as they'd all likely need to be on a lower-calorie diet, as indoor cats don't get as much exercise.
   
Second: What's your schedule like? Is it early out-late in, or irregular? If I know this, I may be able to make suggestions on how to balance the five of them.
   
Third: Feed the cats half dry & half canned (canned in the morning & when you get home). This increases their water intake, which is very good for Ned. This way, you can also make sure Bob gets more calories until he's about a year old.
   
Fourth: If you don't have cat trees, get or build some (not really hard, I did it); they can be extra exercise, good for all. There are plans available online: search "cat plans; tree OR tower OR furniture" & review the results.
   
Ned: A urinary tract support recipe for Ned can be eaten by all the other cats with no real problems & may prevent future problems. ==> A link to a vet's website on the subject of bladder stones is below. The site states that Potassium Citrate can inhibit stones/crystals; also vitamin B-6. Read the whole page, it's very informative, & you may be able to give Ned supplements to help him along, & worry less about the food he's eating (ask your vet about this).
   
Bob: If Bob is over 7 months old, he can eat adult-level food. You can add some rice to Bob's canned food, to help firm up his stool; use cooked brown rice, a teaspoon or so with his canned food in the morning & evening. Also, sensitive-stomach cats generally do well with lamb-based cat food & all the cats can eat that.
   
For Gracie, a "light" food, low-calorie, is good. If Andy & Izzy eat it also, it won't hurt them & will probably help them maintain their weight.
   
Bob can eat Light food too, but I'd supplement his meals with a half-can of regular adult food daily (when you get home at night) until he's 10-12 months old, then he can default to the light diet.
   
The rest: All the cats can eat a Sensitive Stomach recipe.
   
So, all this being said, I THINK that a Sensitive Stomach diet may be the best all-around food. It tends to be higher in protein & lower in fat, which is also good for cats on a diet. There are numerous brands in Petsmart that have a Sensitive Stomach recipe. Add in the canned AM & PM, with extra for Bob for now.
   
Check the percentages of Protein & Fat on the side of the various brands' bags & make your best judgement.
   
When changing a cat's dry diet, mix 1/4 of the new food with 3/4 of the old food, then gradually work up to all new diet.
   
I have yet to see a cat that turns down canned cat food.

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