Lately, though, I've become a little dissatisfied with the locative. It's really not all that useful as a separate case. So I've been thinking of dumping the possessive adjectives and replacing the locative with a good old-fashioned genitive case. Directions and locations would be expressed by the oblique with prepositions. The genitive could take prepositions to show different kinds of possession. Some prepositions could take either an oblique or a genitive, depending on whether it applies to the verb or another noun (e.g. the Ílion for "at" could be used with an oblique noun to show the location of the action, or with a genitive to show where a certain participant is located)--here, the genitive would be more of a general "noun that modifies another noun" case rather than a possessive case. I really like this idea.
However, I can't think of what a nominalized verb phrase would do in the genitive. Here's where my preference for symmetry kicks in--I want it to be possible to put a nominalized clause in any case and have it be usable. It annoys me that I can't make this fit, especially since one of my goals with this language is for it to have a fairly small, regular grammar that can be summarized clearly in about a page or two. I don't want many exceptions and special cases. I'm already kind of fudging things with the verb voices and tenses.