I do love your posts, Strato
You can write a recommendation for high-res mode in the opening post of the thread in which you upload your pack. 
That's it.
You could also do a pre-screen on the first level. In fact, that's almost certainly the best way to do it because it can simply be breezed past if the player wants to ignore it, and it doesn't have the jarring "huh? what's this??" factor of a more-official-looking popup window. That being the case,
I retract any suggestions of popups/recommendations beyond the levelpack's OP and what's already possible via preview screens.
The player is your "customer"... You can't make any decisions on how they should enjoy your "product".
You can, to some extent. For example, if you want to play
Super Mario Odyssey, you need a Nintendo Switch, which is one of Nintendo's least-customisable products to date, and that's saying something!
However, I understand the sentiment behind what you're saying. Someone may need a Switch to play
Odyssey but Nintendo can't tell the player not to play it in the back garden whilst covered in raspberry jam!
Instead, the fact that new backroutes constantly pop up demonstrates that NeoLemmix is much closer to "death of the author" than to "authorial intent"
...
The author simply no longer has any influence on it
I get that. There is a certain amount of "well, it doesn't belong to me anymore" when you release a creative product. It's subject to all kinds of criticism, adulation, analysis, imitation, and any other way that such things can be responded to by a mass audience.
God grant me the serenity to accept the things I cannot change,
courage to change the things I can,
and wisdom to know the difference.
Amen, brother. If only.
