For me it's more a question of design and balance, with some concern for practicality and realism due to a desire for some degree of verisimilitude.
Verisimilitude I think is pretty easy. Leaving pure historical realism arguments aside, it seems within the realm of plausibility that a convenient handless lamp
could exist in a quasi-medieval setting. Discussions about light angle and heat and jostling of the flame and such can be shunted to the same place we discuss wet bowstrings and wielding pikes out of formation and the like. You
could have a device like this in your setting if you wanted it, and it likely wouldn't feel too out of place.
With regards to balance, it's an interesting conundrum. On some level, the game is balanced (so much as it is) on the notion that build components (spells chosen, racial/species characteristics, combat strategy and free hands) have an opportunity cost. Get one, you don't get another. Get one, it will grant a benefit that others don't get (or has some kind of cost). On that level, it feels like there ought to be a cost to not getting darkvision or a light spell, if only that you need a free hand to hold a lantern. At the same time, it isn't a universal notion that someone shouldn't be able to acquire in-game benefits through clever work or GP expenditure just because someone else paid for the same with build resources. Likewise (and simply from a 'will it really matter?' framing), we all know DMs that simply don't have darkness show up in their games as reasonable challenges and the balance isn't obviously irreparably broken -- people still pick species with darkvision, classes with
light, etc. etc.
Yes, light and darkness is something that I personally care about as a GM (unlimited cantrips and lots of darkvision/devils sight don't make it easy, ofc).
I feel like this is the cart in front of the horse. If you figure out a way to make your preferences work with the light cantrip, it'll work fine with an expensive tool solution as well.
But the problem isn't created out of nothing- it's created by players wanting an advantage to help defeat challenges, and the GM considering the feasibility of such advantages while also weighing them against the challenges... just as with any other case of adjudication in GMing
Right. I think everyone understands that and is trying to offer suggestions with regards to it. One primary issue with adjudicating something like this is that the stakes are so low. If you grant it, the players of characters with other ways of achieving the same thing might feel their not-very-significant efforts were wasted. If you decline to grant it, someone has to hold the lantern. The advantage is the low consequences, but that means it's hard to decide how to proceed on balance, fairness, or reasonability concerns (probably one of the reasons people trend towards verisimilitude as a gauge).
More broadly, players thinking creatively and offering suggestions on how they should be able to approach problems in the game world is probably one of the more fun aspects of being a DM. It runs into the same pitfalls as any other aspect (one person's obvious is another's ridiculous, it's 'perfectly reasonable' that create water should be able to create it in your opponent's lungs, etc.). However, it's so much more rewarding than trying to rule on hyper parsing of rules text or something like that. I absolutely love it when the players are rolling barrels down hills at their enemies or dropping rocks in the water pits to raise the water level up to them or proposing ingenious inventions the tinker character can whip up instead of solving the problem through the perfect build or the most math or the like.
