NEW SPELLS which cause additional/ continuous damage: FIRE and / or ACID SPELLS!

Ciao everyone, was thinking that a cool thing to add to offense is the possibility (ideally with a spell, or maybe even an upgrade) to have attacking troops KEEP DOING CONTINUOUS DAMAGE even after the troop is dead.

IE: i spawn archers (or barbs, goblins, minions, any other troop), put the 'FIRE' (or ACID) SPELL down and their arrows (or whatever it is they attack with) do not only give the 'regular' damage from hitting the attacked bulding, but under the new spell their hits (wether it's an arrow from an archer, a sword hit from a barb or whatever) do the 'normal damage' and then keep effecting the attacked bulding for 'X' amount of time - more time & added damage x second for each spell upgrade.

so say i'm 48%ing a base, i have 10 troops left, i put them down with said spell, they are killed by defence but.... having put the 'ACID' or 'FIRE' (or similar) spell on the troops, their hits continue corroding / burning / doing damage to the attacked building.

There is similar stuff in games like 'Borderlands' etc, i think it would be really cool to have here too.

let me know what you think!