Do not think of your birth plan as a goal or aim. Your goal/aim is a healthy, safe birth - and the healthy part includes not being traumatised by mass amounts of pain or feeling scared and out of control.
Everything else - hypnobirthing, waterbirth, interventions - these are all tools which will help you get there. Now it's right that there's no sense in using a sledgehammer to crack a nut (that's doing all of the interventions just because when you are having a totally normal, uncomplicated birth with a pain level you're managing fine) BUT if it turns out your baby is less of a nut to be cracked and more of a rock to be smashed, the sledgehammer might be just what you need.
It might be that up until now you've set your heart on the waterbirth and the hypnobirthing being the way that you're going to remain in control and calm, but these are just two tools that you have at your disposal. So absolutely try them out anyway, they might work fine, but you might find that one or both aren't really up to the job. Then you'll be in a better headspace to say yep, I think it's time to move on to something else. Or if the thought of forceps is freaking you out way more than anything else and the doctors/midwives are quite sure it's likely, it might be worth asking for the epidural at around 5-6cm dilation. It can be a very positive experience. Either way, it doesn't matter - there is no better or worse when it comes to the different tools you can pick. Of course they all have pros and cons but it's ultimately about keeping you in control and comfortable. Use what you need! :)
FWIW my DS was in an awkward position - I don't know if he was back to back - and I spent a lot of time in water, only came out near the end and they were talking about episiotomy/forceps and honestly I could not have cared less, they could have put an entire person up inside me to get him out because at that point all I wanted was for it to stop and him to be born. I didn't need either. But it's not necessarily going to be some traumatising experience even if you don't have an epidural.