I'm glad you posted this because I've been having exactly the same thoughts for a couple months now, even before COVID 19. I have kind of a similar personality I think in that the regular office grind wears me down after a while and I also have a young family at home.
The practice you're talking about in your third to last paragraph is not so far off to how I envision mine running eventually. It's partially how I run it now, but with only one staff member. What I find works for me, though, is spending mornings at home and then going into the office in the afternoon. I find that I'm very focused in the morning, but will tend to get distracted or end work early if I stay for the afternoon (we had a couple bring sunny afternoons last month on which I enjoyed building a couple new raised beds and cages for a vegetable garden but didn't get so much lawyering done...).
I also find if I work in the morning, I actually kind of look forward to going into the office in the afternoon because it provides me with a change of pace and enables me to get those in-person things done. I get driven to distraction somewhat easily and I find splitting the day in half like this helps a lot with restlessness. At the same time, I can still have lunch with my wife and kids and it's easy to cover for my wife for a half hour here and there if she has to go for a doctor appointment or pick up some groceries, etc. Often I can keep working while covering for her (since I'm really just there to make sure the kids don't escape or set the house on fire), so she can run her errand by herself and I can still be productive and be with my family. Most of my client appointments are scheduled for afternoons anyway, since I like to spend the mornings doing lawyerly things like answering emails and reviewing draft docs, etc. regardless of whether I'm at the office. So I don't miss a lot from being at home in my "tiny office" as my eldest son calls it (although I'm writing this post while I'm working from home, so maybe don't completely rely on this...).
Finally, the main thing I like about working from home is that it motivates me to work right away. If I'm at home, I'll usually start my workday around 7:30am, whereas if I'm going into the office in the morning I can't seem to motivate myself to leave any earlier than 8:30am and then I can't focus until well after 9:00am. That's a huge amount of wasted time that I end up having to tack on to the end of the day, so instead of leaving work at 5:30pm and coming home in time for dinner, I'm leaving at 7:00pm and the kids are now in bed. I know this is a personality defect more than a law practice logistical issue, but I've seen the most success personally from working from home in the AM and from the office in the PM (my office is about a 6 or 7 minute drive for me; I get that this wouldn't work as well for everyone). I agree that taking short breaks periodically and moving to another space helps a lot (if I'm trying to work through something ponderous, I'll sometimes walk around my meeting room or reception area and talk it out to myself to the horror, I'm sure, of my assistant. Thank God I'm my own boss).
I think I've already posted ad nauseum about my tech setup, so I'll spare you. But in terms of feeling more connected with the "big office", I've been toying with the idea of having a virtual meeting space setup through Microsoft Teams (which is part of my 365 subscription) so that my assistant and I can talk face-to-face at any time just like if I were in-office (i.e. not video calls, but an ongoing video conference room we can check in and out of as we please). I think this would require a hardware upgrade for my assistant's computer, but it would feel more immediate and personal than her having to phone or email and it would be secure.
I think there are still a couple of practical, non-personality based barriers to total work from home. One of them is the appearance of legitimacy. Most of my clients are older and I think they would be uncomfortable without a real, brick and morter presence and in-person meetings. But this kind of thing is wearing away over time - I'm pretty sure some of my young clients wouldn't care too much if I worked out of my car. That said, there are always going to be reasons for someone to be in-office during the day (accepting deliveries, taking payments from clients, etc.).
In terms of trust and bank stuff, I think that's solvable. Use the LVTS where possible and print and sign your own trust cheques from home where necessary. The staff member who would be making the bank run anyway can stop by home and pick up the cheques (or you could make a single delivery to the office yourself if you're nearby). Printing cheques is one of those admin tasks that I do myself and I find it takes almost no time at all if your're: a) proficient with the software; and b) using alternatives to cheques, where possible. Alternatively, a staff member can just prepare the cheque electronically and email it to you for printing at home (although this solution could create additional admin/bookkeeping headaches). Obviously, having a partner would help here a lot (likewise for helping to supervise transactions if you have a deal closing and you're working from home).
I hope you're able find a more permanent WFH solution for yourself. Luckily, it's the kind of thing that can be done in stages and a lot of people are getting a baptism by fire right now. My setup is still evolving all the time and some weeks for one reason or another I actually end up doing no WFH. But for me, it's about having the flexibility to do it relatively easily whenever I want (I usually make the decision after breakfast. I rarely know when I wake up that I'll be spending the morning at home). But there are days when I'm sure it has improved my productivity and enjoyment of my job plus I've seen benefits in my home-life.