I have been reading some of my older codices recently and stumbled across Witch-Hunters and Daemon-Hunters.
After re-reading the books my interest was sparked once again but after trawling the webway I found nothing on forums or official sites to suggest that there is going to be more from GW concerning the Inquisition.
With this in mind I have started to put together an unofficial codex for use in friendly games.
The basic Idea is that all the units will use stats and points costs of units from other codices. They will simply have different special rules and names. (For example, the deathwatch kill-team is essentially a sternguard squad with a few tweaks)

So far this is the army list that I have put together.

HQ
Inquisitor Lord (1)
• Mandatory HQ option. Must choose one of the 4 inquisitorial paths. Hereticus, Xenos, Malleus or Sigillus*.

Inquisitorial Henchmen. Numbers between 3-12. Options are; Warrior, Bound Daemonhost, Death Cult Assassin, Servitor, Acolyte, Familiar, Chirurgeon
• Do not take up a HQ slot. Maximum of 3 of any type of henchmen. Any bonuses they confer do not stack

Master Assassin (0-1)
• Only available to Sigillus Inquisitors. They must be from a specific temple

Grey Knight Brother Captain (0-1)
• Only Available to Malleus Inquisitors

Adepta Sororitas Heroine (0-1)
• Only Available to Hereticus Inquisitors

Deathwatch Brother Captain (0-1)
• Only Available to Xenos Inquisitors

Priests (0-5 Do not take up a HQ slot)
• Do not take up a HQ slot. Each priest must be attached to a different unit. They Can not be attached to Ordo specific units (such as deathwatch)

Dedicated Transports – Rhino, Chimaera, Land Raider
• Optional transports for HQ/Elite/Troop choices and any attached independent special characters. They can gain specific upgrades dependant on your Inquisitors Ordo

ELITE
Grey Knight Squad
(0-2 Sigillus, 0-3 Malleus, 0 Xenos/Hereticus)
• Follow the above constrictions on unit amounts. Dependant on your Inquisitor Lords Alliegance

Battle Sisters Squad
(0-2 Sigillus, 0-3 Hereticus, 0 Malleus/Xenos)
• Follow the above constrictions on unit amounts. Dependant on your Inquisitor Lords Alliegance

Deathwatch Kill Team
(0-2 Sigillus, 0-3 Xenos, 0 Hereticus/Malleus)
• Follow the above constrictions on unit amounts. Dependant on your Inquisitor Lords Alliegance

Officio Assassinorum Operative (0-2)
• Must be from a specific temple

TROOPS
Inquisitorial Stormtroopers
• Elite troopers that have been trained to work alongside Inquisitors

Adeptus Arbites Enforcers
• Lawkeepers of the local planet/population

Conscripted Guardsmen
• Standard Guardsmen that have been conscripted by the Inquisitor

Penal Legion (0-1)
• Repentant prisoners often used as cannon fodder or meat shields

FAST ATTACK
Arco-Flagellants
• Special rules concerning trigger words

Arbites Bikers
• Arbites Enforcers on bikes

Valkyrie Gunship
• Requisitioned by the inquisitor or a personal transport

Strike Team
• A team of specially armed stormtroopers mounted in a rhino. Three different specs. Blitz/Search & Destroy/Reinforce. This is bought as one package for one set amount of points

HEAVY SUPPORT
Orbital Strike (0-1)
• May only be used if the Inquisitor is on the table

Manticore/Deathstrike Missile Launcher
• Requisitioned by the inquisitor

Redemptionists
• Stormtrooper squadron armed with a variety of Heavy Weapons

Penitent Engine
• A walker containing the body of a traitor (or similar) who fights to prove his loyalty to the Emperor

*As a side note, Sigillus Inquisitors are something of my own creation. They are inquisitors that perhaps trained with one of the three major ordos but have decided to go "free agent" so that they can fight a broader scope of the emperors enemies. Whilst not an official ordo, the background will state that their numbers are growing.

Any questions or comments please post.