This is a boxwood shrub that was 5 feet/1-1/2 meters when we bought the house in 1986. I cut it back every couple of years and last fall cut it way back, than dug it up in April. A lot of it has died back but there is quite a bit of foliage coming out now, as well as the lower branches which were green all winter.

So, I need to develop a plan. I have never been a fan of deadwood on a bonsai, but it seems a shame to cut all of it off. On the other hand, it weighs so much as is that I can't move it around, so I think I need to cut a lot off just to manage it.

So I need an artistic plan and an action plan. When do I root prune and branch prune an evergreen with leaves? What directions are possible here?

I don't have a plan yet, but it will include A LOT of deadwood for sure.
Working in that deadwood with a Dremel will give it personality, patina and it will be much more lighter afterwards.
IF it were mine, I would go for it!

My idea: chop it at least by 2/3, that will improve the overall feel. Then start to create a lot of deadwood features.
Take care: when you prune/chop always leave some leafs, boxwood doesn't bud again if you cut off all the green

Prune roots and branches in early spring.

I dug up a 30 year old boxwood in the spring. I pruned it all the way down so it didn't have any green leaves. 3 months later it has sprouted new branches everywhere. So it is possible.

Dead wood on Box is perfectly acceptable as it does this naturally. I have a Box that is at least 200 years old, we know where it came from and is has deadwood . I will be carving some of it soon. I can't see much of it but I would not be losing the deadwood without much thought. I re potted mine in late spring.

Thanks to all. I was looking at it last night and found a lot of little leaves popping out of what I thought was dead wood. This may complicate the design some.

I am going to take pictures from different angles and then experiment with photo shop taking things out and see what I think. There are two long trunks and a couple of side branches. I think take the side branches off, cut one trunk back to living, and carve the other trunk, but that will just take some time to let the ideas evolve. It is early summer here, which means there will be no major work done until February. I may cut some dead wood off and carve some, but I have to plan first. Rule: you can cut it off but you can't cut it on.

I have to take a lot of wood off simply because it is too heavy. I had to carry it to the back on a two wheel hand cart and then had to put it on its side and slide it into the tub it is in now. That damaged a couple of branches but I can't do that again.