D&D 5E "Make a Strength (History) roll."

[Charlaquin]

It seems to me that this was the essential sticking point: that allowing players to propose a proficiency after the DM had called for an ability check would incentivise players to always try to go for the proficiency regardless of applicability (hence, “gaming the system”).

If this isn’t the point of disagreement, I’m not sure what is. Is the concern simply that allowing the PC to propose a proficiency after the DM calls for an ability roll will slow down play?

Mostly. It also incentives slightly a different approach to action declaration. If action descriptions can be amended after a roll is called for, then the optimal line of play is to describe an action you think will be likely to result in automatic success, without any particular consideration for your character’s proficiencies. Then, if a roll does end up being called for, amend the action to justify applying one of your proficiencies. If action descriptions can’t be amended after a roll is called for, the optimal line of play is to consider your proficiencies when deciding how to act, and describe an action that you think will be likely to result in automatic success, and that you will have a decent chance to succeed at if a roll becomes necessary. The latter also makes for smoother play as the conversation of play always goes description -> resolution -> description instead of sometimes going description -> negotiation -> resolution -> description.

 

[ECMO3]

One of the tools available to GMs and players in 5E is non-standard combinations of ability scores and proficiencies. It doesn't come up very often in my experience, but sometimes odd pairings make for interesting moments in play -- or, rather, interesting moments in play call for the odd pairings. I remember having PCs make Charisma (Athletics) checks to entertain a crowd in the arena, and have sometimes let them make things like Intelligence (Stealth) to try and surmise how an assassin or thief infiltrated a crime scene.

Relatedly, I sometimes let players make checks with proficiency based on their backgrounds or their class (and choosing an appropriate ability score). The 5E proficiency list is narrow and specific and sometimes it is easier to lean on "secondary skills" from the AD&D days.

What are your thoughts on non-standard proficiency and ability scores?

I think they are ok, and if you do it, then this is the way - If you have proficiency in Athletics then you add PB to Charisma (Athletics).

I am not a huge fan of the examples you provided though. I think the first example "to entertain a crowd" would be a performance check. Perhaps Strength (Performance).

The second example should be investigation in my opinion. Intelligence (Stealth) would be more narroly focused on "where is a good place to hide", although I could see either intelligence or isdom for that.