When a Bard boosts CHA s/he boosts her core performance (ie casting).Both INT and Cha mean something I never said they didn't. There is no reason a fighter can't have a high intelligence or a high charisma or both.
@Minigiant has repeatedly suggested that a warlord or similar battle captain character would be more viable if by boosting INT or CHA the character boosted his/her core performance (ie being a battle captain).
Right. So you dump STR and CON.I am playing a fighter (Arcane Archer) right now with starting stats of S8,D16,C10,I15,W12,Ch14
I don't know if @Minigiant or any other poster agrees, but to mind the quintessential battle captain - say, Faramir - is capable in melee. In D&D that means STR and CON can't easily be dumped while retaining that capability. (I guess some battle captains might be high-DEX musketeer types, but clearly that's not Faramir or Eomer or Richard the Lionheart or Jeanne D'Arc or a range of other exemplars a player might draw inspiration from.)
The basic framework of the D&D ability scores probably isn't going to be changed at this point. But it's trivial to change other parts of the game to better fit with them. Allowing a battle captain to use INT or CHA to support combat in some fashion - yet to be fully specified, but obviously some options are being canvassed in this thread - reduces the pressure to ignore those stats in order to ensure viability at the character's key role.
The logic of using STR for Intimidation is that - in the genre, and perhaps in real life too - Fafhrd is more intimidating than The Grey Mouser. And the way to achieve this in D&D, given the stat framework as it currently stands, is to allow the use of STR for Intimidation.There is a rule permitting Fighters and Barbarians and any characters for that matter to make strength(intimidation) checks. It is a variant skill check and is covered in the PHB on page 175. It is rarely used in my games and does not make a lot of sense to me personally but the rules are there if you need it in your games. I do not understand why it should logically be limited to fighters and barbarians though.
The reason for limiting it to those characters would be the same as the reason for any other class specialisation: it gives players of those characters something they can be distinctively good at (compared to, say, rangers and paladins). In the fiction, you could suppose that barbarians and fighters, being the toughest warriors, present the most fearsom demeanours.