I think it's OK to have a melee and a ranged slot.
Having several slots you can fill as you want would also be OK, such as BG1+2, though most players would use melee plus ranged anyway.
We should absolutely not be able to switch equipment during combat outside of switching between different weapon slots.
I like playing melee character and I'd love being able to Swap between 2H and 1H+Shield when required by the situation.
A strenght melee character will have a terrible %to hit with ranged weapons... Maybe it's Time to use dash/ready/dodge or any other utility skills/items instead of using a bow with someone who doesn't know how to aim.
You're right : most players will have a ranged + a melee weapon... But that should be a choice.
Another exemple is when we'll have a lot of powerfull stuff. Being able to swap between weapons that have different properties could be usefull (ennemies having elemental or magical resistance,...)
