Is there a reason for champion MR to not start at 0?
To start, I'd like to state that this could probably be said for armor, but I think that gets slightly more confusing. In light of that, I want to focus exclusively on magic resistance because it's easier to explain.
Assuming the lolwiki is correct, the base for all champions magic resistance is 30. This translates into roughly about 25% percent reduced damage. If this is the standard for all champions, wouldn't it be significantly clearer if simply everyone started at 0 MR / 0% resistance (then +per level thereafter), and monsters/turrets/minions to be adjusted in accordance with that so that spells values are roughly equal? I ask this both because I wonder if there's more complex math involved with it that might not be so obvious, and because I think it's a solution to a problem.
While I understand that basically after level 1 (or even at level 1 with many rune/mastery setups) the number deviates wildly between champion types due to innate scaling/runes/masteries/items, it seems like this might be a change that's preferable. As it is, it seems like a popular complaint is that penetration is currently too strong, and I'm wondering if the fact that resistances don't start from a neutral point, that this might be a reason it's hard to balance penetration. Think of a situation where neither you nor your own opponent have any MR runes/masteries/items. If you're both mid laners and you buy spell penetration even though your opponent has no bonus MR, you still deal more damage to them with those boots. This makes penetration a strong buy for against targets who buy MR and those who not. However, if we were using the system where everyone started off with 0 magic resistance, it would would make the item strong versus target who buy MR (or are naturally tanky) but not against targets who buy exclusively damage items. The reason this might be nice is because this means penetration becomes a stat that's not universally strong, but one that's focused against champions that actually obtain resistances. Because it becomes a stat where there is a focus, its value versus other targets become weaker. You effectively choose to either deal more damage to a tanky target and less to glass cannon than on live, or to ignore spell penetration in favor of damage/bulk in order to deal more damage to glass cannons, but less to tanks.
Please, if there are any obvious errors with my math/typing, point them out. It's really early and this thought kinda came out of nowhere.