I think you are being overly concerned about composite construction.
Just because the beach is made up of stones/cobbles/rocks doesn't mean you are going to break your boat every time you get in or out, unless of course your egress technique is to paddle fast at the beach to try and get your boat as far out of the water as possibe? You may find you often set out with wet feet from wading into ankle deep water to try and get in afloat (I find placing the cockpit next to a rock you can put your hand on for support whilst climbing in and out works for me). With a whitewater background you are probably reasonably proficient at climbing in and out from steep banks/large rocks, no reason you can't do that with a sea kayak too, if you can find a suitable feature that you can float alongside. Obviously if you expect to always be launching and landing in rough conditions where these techniques aeren't possible you may have a little more to worry about.
Composite boats can be quite tough, even when the gel coat chips the actually laminate often remains intact, and when it does finally split, repair is relatively simple.
I made a slight error of judgement on Christmas eve in my WWR (lightly constructed race boat). I was on the river Ewe and knew the rapid under the bridge at the takeout is tidal, but I'd forgotten to check the tides (got up late, running out of time) and gets much harder at lower water levels when more rocks are uncovered. Being on my own, I park at the take out, walk upstream for 15-20 minutes unti lthe river flattens off, and then paddle up to the loch (about 20 minutes) before turning round and paddling back to the car, including the rapids, at race speed (another 20 minutes). I had seen the water level was low and the final rapid didn't appear feasible on the right due to some ledges being uncovered but it looked like there was a narrow slot on the left that was deep enough all the way down to the sea. I decided not to run it and started walking. By the time I had walked and paddled to start my descent, I had decided that I hadn't seen the river (which I don't know very well) so low before, and that the tide was probably coming back in - after all I was going to arrive an hour after I'd left. I was still going to stop above the bridge. The descent went fairly well except I tapped the tail running one of the rapids/weirs above the bridge (long skinny boats often smack the last foot of the stern on pourovers that shorter boats glide smoothly over) and as I got to my finish point I changed my mind and steered for the left of the final rapid. I didn't quite get far enough left- that channel down the first steep bit was closer to the bank than I thought, there was an obvious rock sticking up that I slid to the right of, which I should have been left of (after looking again afterwards), which meant I slid over a couple of smooth barely covered boulders before dropping into the channel (another tail tap). Once in the channel I thought I needed to turn 70 degrees left as I got to the bridge, in fact the water coming down the left channel (spilling off the first ledge) made the turn for me, and then some - I quickly realised I had turned more than 90 degrees in a confined channel, in a boat with limited manouevrability (edge steering like a sea kayak) still travelling close to race pace. I edged hard and put in a couple of big left sweeps but it was too little too late, I just kept the speed up as the bow crashed into the left rock wall and the stern slid downstream past it tipping me. Fearful that the boat would not fit sideways in the channel I must have started ejecting before I realised it was still moving and tried to roll because I was half out of the seat and failed. As I swam up next to the boat, we dropped down the final ramp into the final stopper and I briefly lost contact with the boat before swimming back to it, and to the shore, where I ended up agaisnt a cliff perched on a rock, first curling and then see-sawing the boat to get it nearly empty before climbing back in to find a better place to egress. What had actually happened was that low tide was within 5 minutes of when I actually ran the rapid, at it's most difficult! Oops!
At this point I knew I would have some repairs to do, but walked up and over the bridge to the car, changed, had an initial look over the boat and was surprised how little damage I found. There was a 2-3" 'scrape' on the bow where it hit the wall - right through the outer layer of carbon/kevlar, but this is a relatively highimpact area that had been repaired before, and it did not look as though the filler underneath where I had reshaped it previously was damaged enough to leak. At the stern there were about 3 splits from the tail taps, the longest about 4 or 5" long - these are again common damages for these kind of boats and were actually splits in a repair I did in Switzerland last year. I ran my hand over the hull around the cockpit area, there were some scrapes, but I couldn't feel any obvious splits. In fact a few days later (after I had repaired the ends) I noticed the split from inside the boat just in front of the seat - it had barely been weeping and I had been training at Grandtully in high water so was expecting a bit of seepage through my spray deck and cag anyway. Really nothing serious and again very easy to repair on the inside, and I just filled the scrapes on the outside including the one that corresponded to the split. Today it was perfectly dry again, apart from one wet foot print from me getting in!
Bearing in mind the boat is much more lightly constructed than any sea kayak, and the speed I ran over the boulders and then hit the wall at, I would have expected to need much more extensive repairs, I still think I was lucky it did fit down the channel sideways because that would have broken it in half I'm sure, but even so don't understimate the resilience of a composite boat.
Finally, I rememered as I was carrying my boat back to the car that I have rock guards in the car to use when training on rocky rivers but had forgotten to fit them (simple carbon/kevlar shoe that is moulded over the bow and stern that you can tape in place for training and remove for racing) - if I'd had them on, the bow and stern impacts would have probably only damaged them and not the boat. Most people don't use them on sea kayaks (I have one for the bow of my Taran) but a lot of people do fit a sacrificial strip of glass or kevlar tape as a keel strip, or use keeleasy for the same job - again something like that would normally take the damage rather than the boat.
I like composite boats and may be slightly biased.