I'd like to change that with a house rule, so that tanking Intelligence is at least as unpleasant as tanking Dex or Wis.
Written like that, it's just not possible
Constitution, Dexterity and Wisdom are the "reactive" or "passive" abilities. Nobody cannot choose to avoid using them, as they affect
defense i.e. HP, AC and Perception. So there is not only an incentive to have high scores here, but also clearly to avoid low scores.
To make Intelligence, Strength and Charisma more on par with the other three, you'd have to make all of them affect defensive/passive/reactive abilities more, anything that you cannot choose not to use. We all know that there are Int/Str/Cha saving throws (or reactive ability checks vs spells) but also that they aren't nearly as frequent as Con/Dex/Wis saves.
This would be a BIG change, but you could consider make all illusion spells require Intelligence saves rather than Wisdom, and all paralysis/petrification (or whatever else makes the target impeded in its movement) spells and effects require a Strength save.
Or even a bigger change, you could consider making Intelligence affect AC or Initiative or Perception, make Strength affect HP, and make Charisma affect Initiative or Perception.
Idea 1: Bonus Proficiencies
It's ok, but IMHO the PCs already have more proficiencies than it's really needed, so the effective boost isn't much.
Now, if you were
limited to a number of
skill proficiencies based on Intelligence, so that for example your Int modifier would increase/lower your total number of skills proficiencies (total = class + race + background), now that would probably make players think twice before dumping Int.
Idea 2: Magic Item Attunement
This is generally a fair idea, but it's always subject to the campaign type (grim'n'gritty vs monty haul), and at low levels it can be very often irrelevant.