Yes, I cut new holes in the pool liner. No I didn't add any reinforcement. Another forum I frequent has many people hard plumbing their Intex regular and ultra frame pools, with no reported problems. One of the main advantages of hard plumbing is the ability to upgrade to normal above ground pool pumps and filters.

If you are worried about it needing reinforcement, find someone who is replacing their pool or liner, and see if you can get either the whole liner or just part of it. You can use this to reinforce the areas you want to add intakes or returns. With yours being a donut, it would be a good idea. If you upgrade to either the regular frame or ultra frame, you could hard plumb. Actually, there is a flexible PVC available, that would handle the movement between the intake/returns, and hard PVC. Unfortunately it does get a bit pricey.

I don't know if you noticed in the pics, I've done a partial bury of the pool. If I'd have had more energy and less pain, I would have gone at least a foot deeper. This has had the effect of stabilizing the pool, even with it only buried to the band. I've had guests with kids in the pool, jumping off the ladder platform. Very little wall movement. Note that Intex doesn't like the idea, probably due to the potential of the legs rusting off below ground level. The pool liner itself will handle the dirt being up against it, no problems. I'll handle the leg problem if/when it happens.