If you dont want to buff turrets

Just remove super minions. They can 1v2 nexus turrets. They're harder to kill than nexus turrets. They're dealing more damage that nexus turrets.

Remove super minions and give some other buff when an inhibitor is destroyed like;

Give minions damage reduction against champions when a inhibitor is down, this way you'll be able to siege nexus turrets when YOU TRY TO SIEGE.

So if you dont push a lane without inhibitor it will still be equal, because minions deal same damage to eachother, but even if you send one of your teammates to push that lane, you will push easier because your minions will take less damage from champions. You will have to use some resource if you want to take nexus turrets.

Give minions speed boost unitill they reach others, that way the lane will push easily but wont be able to take enemy nexus with only 2 superminion waves.

Give each wave an extra siege minion.

JUST DO SOMETHING IM SICK WITH 15 MINUTE GAMES EVEN IF I WIN.