The Crimson Binome
Hero
Would they, though? Or would every rogue still end up with a 20, but they would just have lower Wisdom and Charisma? I guess if you're talking about low-level characters, then they wouldn't see any improvement at level 4 while they save up the points for later.I would disagree with this. Use of this option would actually reduce the disparity between different characters. Fewer character's would have a 20, and more would have 14-16, or maybe an 18.
The difference between having Charisma 12 and Charisma 14 (for a rogue) is already borderline negligible. You would have to make twenty Charisma checks before it's likely to have any impact whatsoever. Likewise for Strength or Intelligence, or possibly even Wisdom depending on scenario and playstyle. Asking a player to throw their points into any other stat is simply a bad deal, for as long as their prime stat is still an option. It doesn't even matter the exchange rate. Prime stats are just that important.
The rules addressed this issue by making the cap low enough that every character can still hit it, probably by level 4 but definitely no later than level 8, so they would be free to diversify after that point. There are other ways to address the problem: Get rid of ASIs entirely, so that everything is set in stone at level 1; Give everyone an 18 in their prime score, and leave random or point buy for the other stats; Force ASIs to be applied in a rigid order (lowest first, +1 to highest and +1 to any other, etc). All of those would solve this issue. Simply changing the exchange rate would not.