+ AA6YQ comments below
Actually there are 4 QPs that weekend, 7qp, inqp, neqp, and Delaware qp.
From a rover perspective, which is what this discussion is about, it really doesn't matter how many QSO parties are on the same day. If a rover is near enough that he could operate from two different QSO parties on the same day a different log will be used for each, whether you're using N1MM+ or another logging program. Thus any overlap of abbreviations doesn't matter.
It seems to me the best solution is for N1MM+ to make the conversion from QSO party county abbreviation to correct ADIF CNTY tag when the log is exported to ADIF. That ADIF log can then be easily uploaded to LOTW.
DXLab could take that ADIF and on import create a myQTHID if one doesn't exist for that state/county.
+ There are two independent challenges here:
1. importing a rover's ADIF log and automatically assigning myQTHIDs
2. importing a state QSO party ADIF log and converting each imported QSO's "county code" to a State and County item for ops pursuing WAS and/or USACA awards
+ Challenge #1 does not require unique "county codes". A missing myQTHID can be fabricated from the QSO's MY_GRIDSQUARE, which ideally N1MM will provide in all contests, as it facilitates accurate submissions to LoTW.
+ As for Challenge #2, the N1MM folks have stated that they will not take on the conversion of "county codes" to State and County items; I am working with Jim AD1C on enabling DXKeeper to provide this function.