Let's say there's a creeper inside the Oven. I think it would be nice if in that case instead of using up gunpowder Oven would kill the creeper. Maybe some other mobs too.

but.. how do you get the creeper inside ? You would have to rebuild your high oven each time ._.

It can spawn there. Otherwise maybe add some kind of a hatch block that can replace brick at the top of furnace and can be opened with redstone. While it's opened Oven loses heat but you can drop mob there... I don't know :(

It can't, scorched bricks do not allow mob spawns. If it can it's a bug

With MFR, you could use Safari Nets to put the Creeper in and then seal the oven back up. Also, if this feature makes it in, I want to suggest that a Supercharged Creeper provides more Gunpowder than a regular one.

I don't really like that idea sorry