You're not on the hook "during a layover" in Hawaii with this proposed embedded reserve language. What it means (at least the way I understand it, and all the details have yet to be fleshed out) that some lines have one duty period on one of the middle work days that's a reserve day. That means you'll do whatever flying gets you to Hawaii, the next duty period you're a reserve, and the following duty period you fly back to the mainland or however you fly back to your base. Your reserve duty period still pays 6 tfp, and unless one of the other guys on Hawaii that day (you probably won't be covering more than 5 or 6 Captains or FOs) calls out sick, you won't do anything for that day's pay. In fact, once the last flight leaves Hawaii, you're off the hook completely. There's nothing else they're allowed to use you for, other than for sick calls of those 5 or 6 guys.
Like I said, all the details haven't been covered yet, but it MAY actually be a really good deal: Fly to Hawaii, layover, cover reserve for a few hours on day two (for 6tfp), layover some more, then fly home on day three. A three day trip, paid for three days, but actually working only two of them. And there will probably only be one guy from each seat per day doing this--it remains to be seen if people will bid FOR this or avoid it. Some people might think it's a good deal to spend one work day in Hawaii, on the hook for a few hours (for over a thousand dollars), then go back to drinking mai-tais.
The reason this is a good idea from a company financial sense is because of what you guys already pointed out: the alternative is if someone is sick, you have to wait until you can deadhead someone in from the mainland, i.e. delay the flight for a minimum of 8 hours (depending on when the next flight to Hawaii is). That'll screw up not only your customers, but the rest of the crew's circadian rhythm and remaining work schedule for their pairing, that particular aircraft's flow (it's not making money anymore), and all the ripple effect felt by other crews, customers, and planes' flows that now get swapped down the road.
Does no other airline actually do anything like this? It seems to make sense for a remote location with only a few bodies there at any given time.
Bubba