Aka, the morde version of gp's gamemode. Only morde's not included. Hah! That... seems unfair. Bring Morde back! Double drag op!
Kinda of reminds me a bit of a map-type me and another guy were punting ideas back and forth on. This was back when jungle champs were strictly better at jungling than non-jungle champs? Ah the olden days... Anyway, one key goal for the map was to reverse lane/jungle roles. Aka, mages/adc's would be meta-ideal in jungles, and caster-pushers/fighter/tanks would be ideal in lanes.
Among other things that would happen on this map is (and this is where your idea rang a bell): You'd have neutral monsters that would just wander into lanes and start harassing random minions/champs. Some might even come with buffs. It was imperative you have strong wave clearing power early, or you'd be overwhelmed.