Why isn't the siege breaker archetype the answer for melee carries?

So I was watching the latest Dev Q/A with Ghostcrawler and I saw a very interesting topic brought up. An audience member on twitch asked if there was any chance more champions that interact with towers would be made. The conversation basically came down to champions that effect towers are a fertile theme for development but weren't really seen as a priority. This of course had me thinking why this siege breaker archetype couldn't just be baked into some existing champions that are on the border of melee carry status. It feels like the perfect answer to what could set melee carries apart from ranged, while also allowing more unique effects in League.

The changes could be as simple as designating certain attacks that now effect champions and towers or building new skills altogether. For example Mordekaiser is on the border of being a real objective control monster, but because he wasn't pushed hard enough in that direction he still falls somewhat flat during the actual siege. 3 ways he could have been changed would be:

1. Mace of Spades now effects towers - Simple and impactful change that means tower up time with Morde is always dangerous.

2. Harvesters of souls - Remove bonus EXP. Instead every minion or monster kill grants X amount of souls up to X. Gain X health regen for each soul. The heath regen bonus triples when near an enemy tower. Champion kills award a full stack. Lose half your souls on death.

3. Harvesters of souls - Remove bonus EXP. Instead every minion or monster kill grants X amount of souls up to X. Mordekaiser's next attack on an enemy tower deals X bonus damage and he loses all souls.

Here you have 3 example of where Mordekaiser could have been tuned to be more of a threat towards objective while also keeping to the flavor of his kit. Q absolutely mauling towers is somewhat boring but effective. It would mean that even if he had less up time on a tower he would still pose a huge threat when he got to an objective. His health regen buff could be a defensive option if his offensive options were to oppressive. The last option is just another offensive option that is less front loaded than ability damage on towers. With option three Morde carries a bomb on his next tower attack, but there is counter play there to in the fact that he is melee and slow. If you don't want him bombing your tower you have to keep him off it. If he wins the push he should be rewarded with devastating your tower.

In closing melee risks more than ranged when it comes to taking towers. Riot wants melee carries to be a thing or at the very least more champ diversity that allows for things like double melee lanes or no marksmen comps. This could be addressed with revamping strong melee champion abilities with tower destruction/control in mind. It is a way to add unique ideas to the game outside of 3 hit passives and dashes, while also putting some more distinction between what a carry is and what they can do.