So I gather, upon rereading your post. I haven't read through the MD cases and statutes regarding such things, but based on your description and the Sitz decision, it seems to me that the MD scheme is a bit more...opaque than what SCOTUS set out in Sitz. Since we're presumably talking about a federal standard, I think we can probably expect something more in line with the Sitz decision than what the MD courts have produced ;)
Even the dissent in Sitz would likely agree that security checkpoints in airports are constitutional - if there was a proper protocol in place that eliminates arbitrary decisions by the screeners.
Presumably, that would be satisfied by subjecting everyone to the same initial level of scrutiny, reserving heightened inquiry for those who meet some well-defined criteria. At a checkpoint, everyone gets stopped, but only the folks whose inspection stickers have lapsed, or smell like booze, or have a pound of dope on the front seat get waved over for an extra chat.
In this case, any screen of a female should be done in private by two female screeners and the subject of the screening should be allowed to have her husband/family member accompany her into the private area. I'm not sure how to handle a female traveling alone.
That seems reasonable, so long as hubby doesn't himself seem to present a threat to safety. If both present grounds for suspicion, it seems reasonable to separate them. As for a woman traveling alone, having two female screeners do the pat down would probably be adequate...
Sitz is pretty open-ended - which is why I don't like it. Countenancing a "checkpoint" for enforcement purposes smacks of "other regimes" to quote the dissent. IMO there is a difference between a border checkpoint (the case the majority relies on to allow these checkpoints) and a DWI checkpoint hundreds of miles from the border. There has to be some probable cause for a warrantless seizure - and the Sitz case eliminates that consideration. I really hate to take issue with Rhenquist and Scalia...but in this case I must.
MD requires that the stop be for informational purposes only, and that the motorist, absent some issue with their driving, be allowed to pass if they don't wind down their window. (Along with other criteria such as ample distance for drivers to legally turn around to avoid the roadblock.)