Are you running a number of eviolites in your deck? Otherwise, I'm seeing Night Spear residual/ Hammerhead take advantage of Fliptini and Stoutland.
As for the Celebi, I can understand both sides of its use. On one hand, it does add consistency to the deck like you say, but on the other hand it makes it easier for your opponent to take their prizes (Which is what you're effectively stalling). If I were to test this deck, I think I'd leave the collecting to Lillipup and just worry about attacking once Stoutland's out.
What's your goal once you've set Stoutland active? Ideally, you'd be using him to slow your opponent down enough to set up your own stuff, then plow through your opponent's unprepared field, no? I'm interested to hear any ideas if you have any. When I try this deck, I think I'm going to test both Landorus EX (can attack immediately as needed), DarkraiEX (Can accelerate from bench, gives Stoutland free retreat if you need to Doggieswap to stall longer), MewtwoEX/Eels (Your opponent's faced with a choice: Kill acceleration, or kill the roadblock. They kill Roadblock, then they have a nuke on their hands. Kill the acceleration, they can't get another catcher for a while to kill the roadblock). This is just my two cents, maybe I'm going about Stoutland the wrong way.
I'm loving the Hugh+Stoutland Combo. It is true your opponent's hand will become HUGE, and if you can make them become desperate enough to discard a healthy amount of supporters to avoid losing their other gear, then Stoutland becomes less needed...I love it.