A good line of thinking... the less is more theory is a good thing... :thinking:
However, when you are dealing with a closed system, you need to somehow replace the things that are automatically replenished in nature, so supplementing is unavoidable in certain situations, and this is one of them.
You can do the suggestions that others have posted here, but all that is going to do is delay things. Even if they work, it's only going to work until things continue to degenerate to the point of where they are no longer sufficient.
The powerheads idea, for example, will help some because increasing surface agitation decreases the dissolved Co2, which results in less carbonic acid production and higher pH. However, if you depend on that (or any similar means) as a solution and they stop working or suffer a power loss, your pH is going to crash catastrophically, since none of these solution affects your alkalinity.
You are going to need to add buffer to your system. I can't think of any other way. Dripping kalk is my favorite way of doing it... it keeps the alkalinity up and replenishes calcium in one swipe.