As this is a pre-testing article as it were I can can discuss more easily the reasons why I have included certain things and not others without being biased by how they actually performed. This means the article will be more useful as a way to appreciate how to go about putting together novel new decks but much less useful at detailing the deck in question. Fortunately with it being a guaranteed lower tier deck the failings of the article don't much matter. Here is my initial list for an affinity infect deck:
Mox Opal
Mox Diamond
Mana Crypt
Glistener Elf
Vector Asp
Virulent Sliver
Virulent Wound
Bonesplitter
Chromatic Star
Arcbound Worker
Signal Pest
Mutagenic Growth
Tragic Slip
Terrarion
Blighted Agent
Ichorclaw Myr
Necropede
Plague Myr
Plague Stinger
Cranial Plating
Throne of Geth
Contagion Clasp
Arcbound Ravager
Tumble Magnet
Tezzerets Gambit
14 Lands
Inkmoth Nexus
Seat of the Synod
Vault of Whispers
Tree of Tales
Ancient Tomb
City of Traitors
Darksteel Citadel
Ancient Den
Great Furnace
Blinkmoth Nexus
Topical Island
Bayou
Underground Sea
Glimmervoid
With all the cheap and good poison and proliferate cards from artifacts, blue, green and black included the deck still had plenty of space. There were some obvious cards to include as filler such as the cheap artifact mana fixing and ramp. With a low land count and both few duals and many colourless lands together with a high coloured card count the Chromatic Star and Terrarion are pretty essential. They also work well with the sacrifice effects in the deck. Springleaf Drum is another cheap colour fixer than has continued use that is made a little better by the non infect creatures in the deck being happier to tap down. Aether Vial was a consideration at this stage as well but is a bit slow for what this deck needs I would wager. The various Mox are all no brainers as well as they fix, ramp and enable (what Crypt lacks in fixing it makes up for in ramp...) Then the obvious equipment come into play, Plating is the reason this deck is viable and is a no brainer. The Bonesplitter is good but less powerful than Rancor, being an artifact and easier to cast however make it the cheap pumper of choice.
The cheap arcbound cards and Signal pest were included as they fit very nicely with the whole theme of the deck, being artifacts and able to pump the other creatures with infect. Although the arcbound guys fail to help the non artifact infectors they work with proliferate nicely and Ravager can end games instantly. Steel Overseer was considered as another pump effect but seemed too slow as well as not working with the non-artifact guys. The final few slots were taken by Tezzeret's Gambit which is easy to cast, gives you more longevity and should help the poison count rise. It isn't really an agro card nor is it cheap enough like Thoughtcast, to be great but given the lack of other poisonous options I am pretty content with it. Tumble Magnet seems pretty good for coming down at the end of you curve and forcing through the last bit of poison. Its synergy with proliferate is neat if not all that huge. My final two spots I filled with Mutagenic Growth and Tragic Slip. Both are used to help force through attacks with your weaker creatures. The Growth is very good as it is always castable and scales very well with infect. Much as I would like to have forced in more green creature pump to help out in combat it is the kind of card that will clog up your hand. In a 40 card deck it is easy to get the ratios of things wrong and I would tend to err on the side of caution with things that require creatures when my creature count is already low. Just two equips and one pump effect (excluding Ravager) may seem a little light and may mean I have less potential power but I believe the consistency boost it offers will be worth the trade off. Tragic Slip is easy to trigger the morbid with and is cheap as chips. Decks like this can just lose the the wrong blockers being in place. It needs coloured mana and has no real synergy with the deck but is the sort of thing you need to be able to win games. Perhaps it would be better as Unsummon as Virulent Wound also requires black.
The worst cards in the deck will be the Virulent Sliver which has poisonous 1 rather than infect and so fails to work well with any of the pump effects on top of being a coloured card. Blinkmoth Nexus might also be too narrow as it only really pumps Inkmoth or gets used as an artifact both of which are quite marginal and perhaps would be better as another fixing land. I have taken some risks with this deck as I know it is already underpowered. Those risks are basically very little longevity and a really thin mana base both in quantity and type. If I find I am losing games to having the wrong coloured mana or just having loads of weak dorks doing nothing then I would cut cards like Blinkmoth and Virulent Sliver for things like City of Brass and beefier cards respectively. My hope is however the deck will consistently make a number of infectors on the first two turns and then either maintain the pressure with a bit of disruption and more guys or end the game suddenly with Plating or Ravager. The best or most important cards in the deck are Cranial Plating, Inkmoth Nexus, Ichorclaw Myr and then probably the other good infectors to include Blighted Agent, Glistener Elf, Necropede, Plagued Myr, Plague Stinger and perhaps even Vector Asp! (which is a tell tale sign in itself about the decks outlook) I'll post how hard I got stomped and by what in the comments when all is done.