Ok, so what I'm getting from alvaro is that he wants some artificial leveling of the playing field, so that a bad team gets advantages to such a degree that it out weighs the skill level and items of the opposing team. To me that's ridiculous. Why does a bad team deserve to have complete and total protection from attack when they're at a single tower. The good team doesn't get this advantage because they're at the front lines protecting themselves and not sitting at their towers.
If one team is simply better than the other one, they should win. I hear a lot of talk about towers becoming useless, but to me that's not an issue if the game is even, both sides can ignore towers equally. If the teams are imbalanced by skill level and strategy, why do we need another mechinism to level the playing field? So what if the other team can waltz into your base and kill you? It's your team's fault for feeding them to the point that they have the gear to be able to do that. And if you aren't feeding them, then you should be able to do the same to them.
I understand not wanting to give the team in the lead more advantages, but rewarding poor play and poor team strategy doesn't seem right to me. Those teams are supposed to lose. Just making the towers do % based damage isn't the answer because it reenforces and solidifies what a team needs to do together. You will never again see someone solo taking out towers with the exception of Regulus and possibly tower farming Rooks(however, I'd be a little scared as melee to get close to a tower like that).
It almost sounds to me like alvaro is complaining more about map design then game mechanics. As most maps do not cluster towers except in a few key places. If you go with % based tower damage, on certain maps, you will be required to have a Regulus to take down certain sections as they would almost certainly kill any melee trying to destroy them. You also have to come up with a solution to what the towers do when certain item or skill effects are in effect, like a QoT shield. How does tower damage effect the shield? Sigil of Vitality(haven't seen it used often) becomes worthless when using it against heavily tower'd areas.
You would be opening up a whole new set of balance questions by changing such a core mechanic to the game. Instead of making towers viable, you make them nearly unstoppable for a solo god.
If that's your intention, then you're simply pushing the teams that HP stack and use group strats to do so 100% of the time instead of in certain situations. HP stacking isn't cured by this at all, it makes it even worse. If I know the tower is going to do 10% damage per shot to me, I want the most HP possible so that if someone shows up I can run out of tower range and still have enough HP to fight that person, because they won't be doing % damage.
I personally think there should be some kind of mechanic where you can replace lost towers. So that if you start getting back into the game, your team can reestablish areas of defense. As it stands now once you lose the towers in an area that area is pretty much a no mans land. The replacement obviously would have to cost gold and would need to be on some kind of timer to prevent spamming and exploitation. Of course I'm sure the next response to this will point out that after a certain point towers aren't very useful, but that's the case for everyone if the teams are evenly matched, if they aren't, nothing should be able to save the losing team by default as alvaro is suggesting.