All right, thanks for your patience, everybody. This is a tricky one, especially since our first tournament in 6e is a Feast of Blades qualifier. Here's where things stand as of now, and where they will stand* for the tournament. Given that, of the two interpretations of the rules, abiding by "GW official model" is unenforceable at a tournament and tends to restrict the fun of hobbyists, and that the only way to deal with the more powerful applications of the other interpretation involves house-ruling (which I am loathe to do), the following interpretation of page 61 will be in effect for our tournaments:
For each undefined power weapon in your army, you may select one of the four options presented in the Warhammer 40,000 rulebook. The weapon must be modeled appropriately, and your selection MUST be included on your army list. Any power weapon not specified on your printed army list will be treated as a generic power sword.
*Note: since the upcoming tournament is a Feast of Blades qualifier, any rules judgments from them will take priority. As such, I would advise restraint; if my ruling today makes you go out and throw a zillion power axes in your list, and then Feast of Blades clarifies a different interpretation of the rule, you'll be out of luck. Naturally, any official FAQ from Games Workshop will likewise have priority over this ruling. It's pretty much the conga line all over again, only with long-term modeling considerations, so just be aware.
Again, thanks for all the input, and for letting me take the time to mull this thing over. Now get back to enjoying the damn game!