I'm putting this in the 40k general forum, but only because this forum gets the most attention. Really, this could go anywhere.
So, it seems to me that list tailoring is widely considered to be one of the worst things you can do, basically a kind of cheating. You should bring the list you bring - tailored to the local meta, but that's apparently ok - and take your wins and losses.
What galls me is that this is actually pretty unrealistic. No real-life military is made of "take-all-comers" lists. Militaries have specialists that are sent into various circumstances with the best equipment, the best intelligence, and the best troops for the job. I understand that the 41st Millenia is supposed to be such a hopelessly huge place that "take-all-comers" warbands do wander around, looking for trouble, but if you look at the 40k fiction there's still a fair amount of "list tailoring" going on. When Dante of the Blood Angels sends a Librarian and his entourage to attempt to blunt a tendril of the Hive Fleet, they bring along the best Marines for the job.
Are there any games out there that make gathering intelligence and building the best list you can "on the fly" part of play? Or are there any variants of 40k that allow for some degree of list tailoring to reflect this reality?