Nemesis Draft is like the lcs

On the basis of the opposing team likely also has less-than-ideal champs, getting past early game is not that bad, since almost everyone else is in the same boat (although theres usually someone playing a meta champ in a meta role wondering what everyone elses problem is).

Really pretty much any ranged champ can be built and played as an AA based adc, and they'll be nearly as effective as a conventional AA focused adc, since the majority of their power comes from their items rather than abilities.

In a similar vein, (and as was rather problematic for awhile on a number of assassins) anyone can build like a tank and be pretty effective as a tank, even if you'd think they're a squishy mage/marksman.

There are very few truly unworkable comps in theory, it's just in practice people don't work as a team and adapt their builds/playstyles to make things work, and instead everyone just focuses on what is appropriate for their particular champion regardless of the role they should be playing (or occasionally they do adapt their builds, but their playstyle is still that of a conventional build, which usually gets them in hot water [protip: ap ali makes a poor tank]).