How about Demelo + Ennis and a 3rd for Johnsson?

Why do the Leaf trade one of their regular RHD, a position of with no depth and fill with an AHLer who would have to learn to play his offside at the NHL level. Trading any Leaf Dman just makes the team worse unless their is equal replacement.

I don't think its really necessary to trade Ceci either, although, I will say that if Dermott gets a chance to play with Rielly on the right side and excels and Sandin pushes enough to warrant bringing him up (Lets be honest, he very well could already be better than Ceci) having Sandin and Holl on the bottom pair, makes Ceci the odd man out. With that said, I agree with @palhal, moving Ceci for nothing is not the best course of action.

Sandin is not coming up this year. Let him get stronger for another year.
Ceci played the most minues in the first two games under Keefe. He's not as bad as everyone says on here , and is a top 4 RHD.
Remember who Holl plays agianst comparded to who Ceci plays against. Can't see Holl going against top lines anytime.

because its the easiest way for people to get under the cap on this site?

That is an easy no for the Leafs. Mango is a 2nd line guy with edge and a good net front presence signed on a good deal with term and you want him for a 3rd pair Dman, a 3rd, and a 4th line forward? We'll pass thanks.

Doesn't mean it's the best way. Trading away a defenceman without getting one back is a bad idea for this team, specifically an RHD. Which is why they got Ceci in the first place, because they needed an RHD back in the Zaitsev deal.