Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you: No adverts like this in the forums anymore. Times and dates in your local timezone. Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance. Email notifications for threads you want to watch closely. Being a part of the oldest wargaming community on the net. If you are already a member then feel free to login now.

Would an old codex Daemonhunters army still be playable in the newest edition of 40k?

The physical models yeah.
The codex... probably not unless you asked.
Even then there would be issues with the codex. Outdated rules and the like...

Maybe, though obviously you'd need to ask your opponent's permission, and I'd imagine that you'd need to tweak it a bit so it's compatible with 6th.

Maybe somebody already has? Try googling around for it.

what kind of list were you thinking of running? I did a psuedo DH list in a game recently. HQ was an inquisitor lord with retinue of inquisitorial storm troopers (acolytes built as close to them as possible) then some GKs for core with some inducted guard(allied force) vindicare for the elite choice. ect.

though if you wanted to do a radicle Inqusitor list or an all storm trooper list you would need that book

I'd say just ask your opponent. the only thing they would have to get used to is the shinny armor rule and the fact that your grey knights would be fearless.(but slightly more expensive)

The vast majority of daemonhunter's stuff can be pulled off with the grey knight's book and a bit of imagination.

I was thinking of trying an all mech list with an inquisitor lord and storm troopers in rhinos, more storm troopers in rhinos and some assasins with some grey knight squads deep striking.

What could I do to update the book to meet 6th edition standards?

Easiest way would be just using the Grey Knight codex, making your Inquisitor Lord a count-as Coteaz, and using Warrior Acolytes with carapace armour and hot-shot lasguns as count-as storm troopers.

You'd then have a fluffy army with a full set of serviceable rules without having to get in rule arguments.