As the ED you are free to use whatever rules you see fit - of course, you must balance that decision on whatever factors are most important to you. First off, are you changing horses in mid-stream, here - has the contest previously run under the NW rules or is this a newly added event? Would changing the rules now alienate or shut out a significant portion of your previous entry?
If this is a new event, is the complaining coming from one or more who actually have a model that would be locked out? If there is no impact on REAL hardware (as opposed to 'What if ... ' hardware), then perhaps setting the rules to "Denver rules" would make it more attractive to those who already have .15's flying. One other consideration is that you might intend to submit scores for "Top 20" purposes - so you might have to either omit those that don't comply with NCS rules, similar to the way the 10 point bonus for Brodak planes is subtracted (if it was given) from scores from Brodak.
MY goal as ED is to keep the deck busy, first and foremost. So finding whatever means to maximize the entries comes first. If I start getting complaints from my regular contestants, I give their input more weight than I give to questions from "maybe" contestants. My own example is in our .15 event we have a statement that "cross flow" .19's are allowed. This goes back to some local contests that have been flying .15 since it was invented. We have NEVER had anyone enter a .19 powered plane that I can remember (though I did build one around an Enya .19 - just never entered it in a contest), but I have kept the rule in our contest "just in case". If someone were to actually enter one, I would probably not submit that score to NCS for the Top 20, but I would still keep the statement in future contests.