Good input from one and all so far.
As already stated, the parallelism of the theme entries will be key. So, you'll probably have to go with all prefixes or all units, and you'll have to be on the lookout for any odd-man-out situations: E.g., three units that are distances and one which is weight would lack parallelism. Note that the latter can be fixed in various ways: You could stick with all distances; you could go with a couple of each; or you could make no two units the same. Be careful with the intermediate case: some editors may not like it.
You seem to be on the right track building an arsenal of possibilities. I'd say keep building it until something gives. There are numerous ways this theme might play out, but it will all come down to finding the particular examples that fit a pattern. So, don't have a preconceived notion of which pattern might work out: try many of them until you find one which yields the most content.
The other constraining aspect will be theme entry length, so you'll normally have to pair up items (lengthwise). Be advised that if there's an odd number of theme entries, the unpaired one can be either an odd or even number of letters: The latter situation can be handled by having a 16-column puzzle (rather than 15). So, don't be deceived into thinking that all those even ones must be matched up.
Toward generating more content, you can approach it from two ends: You could get a list of celebrities from, say, an almanac and pull out names that are homophones of physical units. But you might also get a list of units and prefixes from Wikipedia so you're familiar with the full list of what's available from that end.
Finally, stick with mainstream content that multiple generations of people will find familiar. That's liable to eliminate the two rappers.
Overall, I like the theme idea. Good luck with it.
Regards,
Joe Krozel
