In the end I decided to go full redundant with a 40AL pony and two regs. I'm going to run the same rig whether solo or partnered and so will go with a 5' hose on my primary second stage.
I think "in the end" is extremely relative. Most of us have switched configurations so many times it's unreal. My basement (and wife) shames me for it every time I walk downstairs.
Do yourself a favor and just log as many hours as you can in the water. I'd much rather dive with someone who has 100 hours and sh!try gear than someone who has 5 hours and the best gear. No matter what you do now, your gear will change after you hit 50 hrs, 100 hrs, 200 hrs...
As for solo diving you're an adult. Only you can know your own limitations. The word "solo" has different meaning for different people. Being 90' deep "solo" in the engine room vs being 20' deep "solo" in a puddle on the platform are very different. Know your limitations and be smart.. listen to that little spidey sense and don't get into scary situations.
From my own experience, "in the end" (so far anyway!) I wound up with 7' long hose, bp/w, set of doubles, in a drysuit.. my gear changes have really come to a crawl (thank goodness!). It's versatile and works in all the diving that I do (mostly cold murky ocean or quarry). It is so nice that the only thing I have to "plan" is what depth and what mix to take. Everything else is the same.
Good luck!!