A number of comments:
1) If you rip out your existing trees and try to plant new ones, with the apples at least, you may have problems with replant disease. (This will stunt your new trees. Commercial growers fumigate the soil to sterilise it to prevent this)
2) You can certainly prune your existing trees to a fruiting wall form, by lopping off all branches which intrude into the alleyways, (and if necessary, fostering the growth of new branches in the plane of the tree row)
3) Commercial apple orchards are now almost all planted with relatively dwarfing rootstocks, supported on trellises, and trained to a flat fruiting wall. Interestingly, these are treated as "crops", with an expectation that they will last 20 years or so, at which time they will be ripped out, (the soil fumigated), and replanted. If you have larger rootstocks, they will last far longer - 100 years for full size roots.
4) In passing, peaches: yes peach trees are relatively short-lived, much shorter than apples.
5) If you do not prune/train to a fruiting wall, a very effective understory management plan is to spread cardboard under the trees, covered by a thick mulch of wood chips, (ideally with "ramial" wood chips, branches up to 2 3/4" in diameter, (see research done at Laval University, in the 80's or 90's)
6) Espalier, properly, involves a lot more than training to a relatively flat plane. It involves both training to a specific geometric pattern and regular summer pruning to encourage development of fruit spurs rather than vegetative growth. (This is not intuitively obvious, but a fruit bud has 5 leaves for each bud, while a vegetative bud has only one. So while the tree is markedly controlled in shape and size, the photosynthesis area is maintained.)
7) If, after all this, you still want to "start afresh", you could consider sawing off the existing trees a couple of feet off the ground, and grafting in new scion wood, (with bark grafts) in the spring. (Place as many scions as will fit comfortably on each stub - that way even if some fail, you are likely to have at least one succeed on each tree. Cut out extras the following year, when you are sure your graft is healthy and solid.) Then carefully prune and train your new growth into whatever shape you fancy. You could also take the opportunity to introduce new cultivars into your orchard.