A number of people like the idea of treating elided places as being {zo'e} or {zi'o} (the earliest proposal I can remember being by And Rosta). I like the idea, but I would go a step further, or rather, I'd like to make things a bit more dependent on the current discourse. What's the problem with having all omitted places be {zo'e}? Well, it fills in values in places we might not even want to fill. This is especially true for bloated gismu, but in general it can be "unclean".
I propose the following procedure for determining what fills an omitted place:
1. At the start of discourse, all places are filled with {zi'o}. {mi citka} as the first sentence of discourse (or a conversation) means {mi citka zi'o}, "I am eating." The difference is that {mi citka zo'e} could mean "I am eating cereal", but {mi citka zi'o} is true no matter what I eat. In this regard, {zi'o} is like a {su'o da} without scope. In another way it's like {ro da}: {ro da zo'u: ga nai mi citka da gi mi citka zi'o}. The important point is that {zi'o} is more general than {zo'e}, and is therefore the better default value for neutral contexts.
2. Once a place of a predicate has been filled, that place will afterwards be filled with {zo'e}. As the first {citka}-sentence of a given discourse, {mi na citka} means "I'm not eating anything." ({mi na citka zi'o}). Once someone says {mi citka lo nanba}, {mi na citka} will be {mi na citka zo'e}, and can (but needn't) be interpreted as "I'm not eating bread".
3. Under certain circumstances, a place can be reset to {zi'o}. Presumably, anytime a place gets filled with a non-{zo'e} non-{zi'o} value, it reverts back to {zi'o} after the sentence ends. I.e. {da}, {ce'u} and possibly {ke'a} reset their places to {zi'o} afterwards.
This flexible procedure makes {zi'o} and {zo'e} behave more intelligently, and allows us to be general more easily when it is more likely to be desired, while making us be explicit a little more often when we actually mean specific things. This will be facilitated by the new anaphora system which we will surely have to adopt sooner or later. (I'm sort of cooking one up at the moment)