Perhaps a solution for this...
Sound Devices MixPre-D
Looking into the MixPre-D it supports iPad, doesn't look like iPhone support. Still a very nice piece of gear.
all fine and good, but the 7 series recorders are only marginally bigger than the mixpre-d and doesn't need another connector to go to the recorder. I'm assuming that since these are paying gigs, you need a professional product at the end.
If you're really trying to put together a run-n-gun-style setup, then I'd look at two things:
1) improving your bag setup for carrying everything. I found I could carry a 722, a sonosax preamp (maybe half the size of the 722), lithium ion battery, cables, various accessories, and small mics all within the Portabrace AR-7 and it's small add on. That much stuff in the AR-7 setup surprised some people when they saw it in the field. Now, it required some forethought about what I was going to pack, but it's very doable if you hunt for a bag that works well with your equipment/purpose. Once I got bag management under control and moved to a smaller bag, life got better in terms of being agile.
2) I'm assuming your "stereo mic" is large diaphragm based in a tube-like structure. If so, then yes, I can understand why you might consider it difficult to do stuff on the go with it. My first thought was a Pearl MSH-10, or the Audio Technica PRO24, or the Rode NT4, all of which are small diaphragm stereo mics and would reduce both size and weight for the mic and shock mount required. The Pro24 even has it's own batteries, no idea how good it is though.
3) Keeping as much setup as possible. Instead of reconnecting cables and putting the mic in the shock, can you figure out a way to leave as much connected and just lay it in a bag so you can whip it out, record a bit, and put it away to move on? Likewise, if you've got other stuff (e.g. laptop, notebook, etc), can you pick a bag that can hold everything instead of multiple bags? I've used a laptop bag before and rearranged it specifically because of this. I hate multiple bags.
So technically the smallest setup would be something like the AT Pro24 and a Sony PCM-10, but I don't know if I'd sign my name on a product created with that, maybe, sure, but I'd want to experiment with it first.
Is it
complexity of the setup that makes it cumbersome
or the physical size? I think this is a critical aspect that I couldn't tease out of your original post. I know people who can hide a 7 series unit on their body and sneak it around places, it's not that big compared to some other pieces of gear we use here, but if size really is the issue, then would you rather have 2 or 3 boxes all connected by cables instead of that 702?