I would say H. crispa is a good choice as well. Often they are imported bleached, or worse yet, dyed a phony looking yellow and in need of tlc. Ethically, I am not sure which is worse, to pass a bleached, but otherwise healthy sebae by or to purchase it and reward the lfs for selling such an animal. Frankly, I think lfs will continue to sell dyed sebaes and bleached sebaes regardless. They've been doing it forever. I suppose the best we can do is at least ask say to the staff: "it would be nice if you only offered healthy, non-dyed anemones for sale." One of my soap boxes. lol On the upside, sebaes can be very hardy and grow large and are a natural host to a very large number of clownfish species.
For the carpets, certainly gigantea would prove challenging for you. You've had years of saltwater experience and apparently are doing well with BTAs and LTAs, so that could prove rewarding. I only have magnificas, so I can't speak from experience, but it seems giganteas are on par with magnificas for difficulty. Also like magnificas, they are beautiful and play host to numerous species of clownfishes including ocellaris and percula.