The following changes should be implemented when possible:

deadly designs = sporogenic infection
A lot more play options here in terms of cure things you can do. I think that people simply won't pay into deadly or it won't be run.

Order of Succession = Kitnap
I think that order is funny, but won't get used most of the time. Also, Kitnap will be gifted a lot more of the time than not I would think, so it should provide an interesting choice.

Plague Reaver = Tinybones, the pickpocket
Plague Reaver and board wiping just isn't super fun. Offering trades with a 1/1 deathtouch that also if you let them through can cast something from yard that can mix up board is big. I think it's a huge improvement in terms of fun and politics

territorial hellkite = vengeful ancestor
smaller body that is more controlled than the previous, BUT it fits the goad mechanic and moves games along more.
Blacksmith's Skill = Take Up the Shield
Seems like it better gives up a trade, but still let's exile go through. I think this is a change back from an earlier inclusion of take up the shield.

Oblation = Argent Dais
Repeatable Oblation seems more fun. Also creates more decisions for if you should attack with 2 or not.

jailbreak = silverquil lecturer
jailbreak looked fun, but just doesn't get cast for the big play you want it to be

trial of a time lord = tempt with bunnies
A more fun card. Trial takes awhile to happen, it is a dr. who card, and it although it does payoff for voting it resets the board rather than adds to board state to make choices more challenging. I think this singular temp card will work, and it feels weak enough that someone will be tempted.

Potentially Varghast = spitting dilophosaurus
Fits the counter theme more and is a bit more exciting of a payoff.

Potentially Mausoleum turnkey = soul snuffers
Would be a bit more -1/-1 counter stuff and also mausoleum feels a little weak for recursion considering opponent can choose, though it fits theme of cube less.

grotesque mutation = devour flesh
More in the vein of black than a combat trick.

Phargax Giant = Taunting Kobold (downshifted)
Taunting kobold downshift to common in place of Paragax Giant, and then add Sontaran General as the uncommon slot

Taunting Kobold (downshifting) = Sontaran General

Bond Beetle = Sunshower Druid
Hopefully the lifegain and +1 toughness will make improve playability.

Goblin Rackateer = Infernal Captor.
I think the threaten will lead to fun gameplay moments and there should be ample targets. On it's own, it's at least a hill giant. The Rackateer just didn't trade favorably at all and could only goad what it was attacking into.

Wall of Shard = Leonin Relic-Warder
Was potentially going to be Tempered Veteran, and it still may be at some point, but I think more enchantmet removal is needed, so it will instead be subbed out for Leonin Relic-Warder

Kindling = Sazacap's Brew
fine on it's own but can have extra interactions with gift. The same idea with the other gift spell

Accumulated Knowledge = Mind Spiral

Muscle Burst = Longstalk Brawl
I am concerned green has too much removal potentially.

Kjeldoran War Cry = Crumb and Get It.