Naturalistic, with each word being taken from the corresponding word in the source languages.
Schematic, with each correlative being predictable from its meaning by a combination of two words, along the lines of Esperanto's system. For example, all of the interrogatives would start with the word vilk, and all correlatives about location end with sted, so where would be vilk sted or literally which place.
Schematic, with all of the correlatives predicable from their function, but more reflective of the reference langs. This is possible due to some schematic-ness already existing for historical reasons. For example, in English, most interrogatives start wh- and most definites start with th-. Some locatives end in -ere, and some correlatives about things end in -at. This accurately predicts "what", "that", "where", and "there" (at least orthographically). A similar pattern exists in other Germanic languages.