Cool idea so I did some calculating:

Odd Paladin: Total Cost 102, which means you could do some slight alteration and fit in Diihall without screwing up your curve too much. I think that drawing an extra card every turn would definitely be worth it and probably overpowered in such a hyper-aggro deck. [https://hsreplay.net/decks/wsEA4huCdRblzBiNfbreWf/]

Odd Rouge: Total Cost 93, I don't know how accurate the winrate data is for the deck post giggling nerf but once again small alterations could be made to fit in Dihall, and the draw engine would probably again be overpowered.

[https://hsreplay.net/decks/GI1BpCBrIfcN48h5fZkTgd/]

Big Spell Mage: Total Cost 145, leaving some wiggle room to fit in Saldo. Surely having a 3/5 on board is a big impact for the early game, and since no huge changes have to be made the deck would probably function as intended, i'd say this is overpowered once again. [https://hsreplay.net/decks/uktkeOicF3e3Gt6Zi3Ziyg/]

I don't even know what kind of deck could fit Zhadn in. Maybe some sort of Giant deck since their original cost would count towards the 200?

Overall, I don't think the slight tweaks that can be made to these top tier decks justify the huge bonus.