That is an interesting idea. They could number the chairs and you can go up to a desk and checkout enough open chairs for your party. They would give you up to 2 hours and ask that you let them know if you are leaving earlier. At the end of 2 hours, you could checkout for another hour at a time if chairs aren't full. I am not sure I support this, since it might complicate things and the best part of cruising is lack of complication, but it is an option worth considering. What I fear is it would turn into is a reservation system versus first-come-first-served, meaning even one less thing you can do spontaneously and have access to as a newer cruiser.
I do think your solution might improve on
@mevelandry proposal, but I'd still vote as Not A Fan.
I don't go on cruises for the activities the ships provide. I use the ship as transportation to sun and fun in the Caribbean and as a means to get a taste of international cities around the world, without having to devote weeks and many hassles to experience them.
Therefore, my onboard activity consists of relaxing beside the pool reading for the day. Is it really nice that I'm expected to give up my pool time (which is my favorite thing to do) to give you a chance at pool time whenever you like, which might only be used to fill a gap in your otherwise busy schedule?
I see adults come out at 6am and put things on chairs and then they don't show up until their excursion returns to the ship in the late afternoon. My idea to stop that, is that you get a timed/different colored card for each hour or two the pool is open. Then pool attendants could come by the chair where the previous color card is and anyone who is not present in the pool area for that upcoming hour, gets their things removed. If you are there, the attendant swaps your card for the new time block.
I think another way to control the pool situation is to have more cubbies for people who only want to swim for a little while. Does a family of 5 people really need 5 chairs? Yet, I see this over and over again, especially on
DCL. I get that the kids don't want to share a chair sometimes, but surely it can be explained that sometimes it's necessary. Most of the times, the kids never are out of the pool long enough to even need a chair, much less one per person.
When the pools are busy, my husband and I will often share a lounger. I go to sit in the pool and he lounges. When I get out, he either goes to the pool, sits on the end of the lounger or goes off to do something else. Even if there are plenty of chairs, we often do this and will get one chair in the shade somewhere and swap off.