[{_id:1,name:"foo",time:[1234],doc:[1234]},{_id:2,name:"alexa",time:[1234],doc:[1234]}]

db.collection.aggregate([{$addFields:{root:{$arrayToObject:[[{k:"$name",v:"$doc"}]]}}},{$group:{_id:null,root:{$mergeObjects:"$root"},time:{$push:"$time"}}},{$addFields:{time:{$reduce:{input:"$time",initialValue:[],in:{$setUnion:["$$this","$$value"]}}}}},{$replaceRoot:{newRoot:{$mergeObjects:["$root",{time:"$time"}]}}}])