'kepeken' and 'ilo' have always been a suspect pair of words. They seem much closer to one another than other word pairs. Yet both are heavily entrenched -- in separate niches -- and, so, when cutting words is an issue, they are never considered in the final phases. The case for joining them goes something like this:
'kepeken', whether as a verb (as of old) or a preposition (nowadays) never followed the pattern that the genus of its objects was called by the same word (like 'moku' for "eat" and "food"). That genus for 'kepeken' was always 'ilo'. As a result, 'kepeken' as a noun was always the deverbative "use, using" (with one possible exception found once: 'pana e kepeken' "give help" ). As a modifier, 'kepeken' seems to be either the descriptive "useful" or the head of a prepositional phrase.
'ilo' is a noun which means "tool, device, engine, machine, computer" and, as such gets modified in various ways for what the device is used for ('ilo sona', 'ilo lape') and, occasionally, what it is like physically ('ilo tawa pi sike tu'). As a modifier, it always means "mechanical, electronic" or some such specific sense. Never just "useful". The verb roles are almost never used and seem to be only in the sense "work on with tools", never "make a tool of, i.e. use" (with one uncertain exception).
Fusing the two into one (I would vote for 'ilo' as noun and preposition) results in a fairly normal tp word, appearing regularly in all sorts of roles with a variety of meanings in each, rather than two rather more limited words (in both role and meaning) which obviously are related but not connected.