Cycle of mimetic Slivers

[Toad]

I have been toying with Slivers a bit lately and thought it would be quite cool to have a cycle of Slivers being clones of existing creatures. This sounds quite flavorful to me, with Slivers escaping the Riptide Laboratory, discovering a new World and adaptating to it by mutating and copying other powerful creatures. My main concern with the cycle is about card rarity. Cycles are made from cards with the same rarity (unless Im mistaken), and my cards wouldnt fit in that scheme.

Flametongue Sliver - 
Creature - Sliver Mutant
All Slivers gain "When this creature comes into play, it may deal damage equal to its power to target creature".
4/2

Mesmeric Sliver - 
Creature - Sliver Horror
All Slivers gain "When this creature comes into play, target opponent reveals his or her hand and you choose a nonland card from it. Remove that card from the game. When this creature leaves play, return the removed card to its owner's hand".
1/1

Phantom Sliver - 
Creature - Sliver Spirit
All Slivers gain "If damage would be dealt to this creature, prevent that damage. Put a -1/-1 counter on this creature".
5/3

Quicksilver Sliver -
Creature - Sliver Shapeshifter
As Quicksilver Sliver comes into play, you may choose a creature in play.
All Slivers gain all activated abilities of the chosen creature. You may spend blue mana as though it were mana of any color to pay the activation costs of these abilities.
3/4

Runed Sliver -
Creature - Sliver Mutant
All Slivers gain: " : Target Sliver you control gains protection from the color of your choice until end of turn".
1/1

I first intented to do a five color Sliver too, but all the other five color creatures are either Slivers, or Legends with their own background.

[Toad]

Current wording

Flametongue Sliver - 
Creature - Sliver Mutant
All Slivers gain "When this creature comes into play, it may deal damage equal to its power to target creature".
4/2

Mesmeric Sliver - 
Creature - Sliver Horror
All Slivers gain "When this creature comes into play, target opponent reveals his or her hand and you choose a nonland card from it. Remove that card from the game. When this creature leaves play, return the removed card to its owner's hand".
1/1

Phantom Sliver - 
Creature - Sliver Spirit
All Slivers gain "If damage would be dealt to this creature, prevent that damage. Put a -1/-1 counter on this creature".
5/3

Quicksilver Sliver -
Creature - Sliver Shapeshifter
As Quicksilver Sliver comes into play, you may choose a creature in play.
All Slivers gain all activated abilities of the chosen creature. You may spend blue mana as though it were mana of any color to pay the activation costs of these abilities.
3/4

Runed Sliver -
Creature - Sliver Mutant
All Slivers gain: " : Target Sliver you control gains protection from the color of your choice until end of turn".
1/1

[Anusien]

Shouldn't Phantom Sliver be white?  I understand both colors got the ability, but it feels more white.  Then again, I wasn't playing back then.  Then again, I don't like the white ability; MoR Sliver feels too weak.  You already have another saving creatures sort of sliver.  Instead at White you could put some sort of tapping or even Mangara/Major Teroh.  All Slivers gain "WW, sacrifice a sliver: Remove target attacking or blocking creature from the game."?

I don't like Quicksilver Sliver; it feels like it could get out of hand way too quickly.  What about giving out Spiketail Hatchling/Drakeling ability or even "All Slivers have: UU, sacrfice a Sliver: Counter target spell."?

Otherwise, solid.