A small buff to Magnetic Field, which would allow Arc Warden to counter a tower dive by fielding an allied tower to grant it the attack boost to fight off enemies.

It would also create some synergy between Arc and Jugger, as he would gain the attack speed during Omnislash.

Besides this, in my opinion, spells which can affect allied buildings should always be able to affect them while invulnerable as well. This is already the case for Bloodlust, Ice Armor, Guardian Angel, Chronosphere and Crimson Guard. Magnetic Field and Living Armor are the only spells which cannot target/affect invulnerable buildings.