Ilbranteloth
Explorer
I think that is a good house rule. It is a significant boost up in the power of magic items though, so a caster can cast invisibility on the rogue and hold the concentration for it. But if the rogue drinks a potion of invisibility then there is no concentration. I think if you mess with one piece of that equation you should mess with both: caster and magic items.
I like the concentration rules for casting spells. They make sense and have a good limiting effect on them. I don't mind looking at ways to alter that (like the feat I mentioned), but those are essentially exceptions in the world, not the norm.
The concentration rules don't make sense to me for drinking a potion. More importantly, I don't mind allowing concentration spells to not require it from a potion because they are consumable, one-time use items and you can't use more than one potion at a time. So at best you're adding one effect. If you have more than one spellcaster you can already stack effects anyway, this just gives you a different avenue.
I'm OK with requiring casting from scrolls, since you're essentially just casting the spell anyway.
Ilbranteloth