Sounds like you had poor treatment last time, and I don't blame you for wanting to avoid that again.
I had emcs with both my DDs, this time I'm having a elcs. I can sympathise with your feeling of things "not being the same", though it's my stomach muscles that took the battering in my case. After each CS I have lost more feeling in my stomach, so now I can barely feel if something is pressing against me, until it hurts quite a lot (nearly stabbed myself with a gimlet last week as a result!). For over a year after each CS, every time I sneezed I would get a pulling type of pain at one side of my scar - when I asked a GP about this, they said it would be the side the stitches had been knotted off at! I used to be able to do lots of digging, lifting etc, not so much now, as my muscles are seriously wrecked, and I just don't have the time I used to have to exercise and build them back up.
I used to know someone who had a bad stitching job done on her after her first baby. She tore again with her second baby, and had a much better job done that time, which actually improved matters to a large extent. Obviously everyone is different, but going with another natural birth worked out well for her.
Can you talk what happened over with one of the supervisors of midwives at the hospital, and explain that this has made you want a CS because it was such a bad experience, perhaps see if you can get assurances that this won't happen again, and and explanation of why it did happen originally? Five years is long enough for policies to have been changed and practices tightened up on. You could specify in your birth plan what you want to happen if you need stitches (e.g. your DH must stay with you, the baby must not be separated from you; whatever would make it more bearable). Get your DH (if you don't feel able to yourself, having just given birth) to remind the mws what you want, and stick to it.
I don't want to sound patronising, as I'm sure you're aware of what happens in a CS, and probably know people who have had one, but CS's aren't without risk. I know a couple of friends who had nasty infections from theirs, plus there's the not driving, not lifting, the painkillers etc.
It's your right to ask for a CS if you really want one, and I don't think they can refuse you (if they do, I think they have to refer you to someone else who will do it).
A friend had a planned CS and went into labour a couple of weeks early. It was in the evening, and they just took her into hospital and did the CS early the next morning. If you were to be very quick in labour, then I don't know what would happen. Again, this would be worth discussing with a midwife. I don't think they would factor in your last baby being early, as I know lots of women who had early first babies and a long wait the second time around. I believe NICE recommends planned CS to be done at 39 weeks, and this seems to be what most hospitals do now. My nearest hospital won't do them until 40 weeks, unless there is medical necessity.
Sorry for writing an essay, and good luck with your choice.