The new Standalone Engine
Most of the issues have to be dealt with by one or two programmers. Rocket’s team are doing all the experimental stuff now (cause that is what pre-production/pre-alpha is all about) – all the big stuff is done now. Combating hacking require an entire re-development of the engine (source). Pre-alpha added all the fundamental changes to the engine. Once that is done, the alpha start and functionality gets added/expanded (source).
ArmA3 is far less of a new engine than DayZ because DayZ has far greater changes in it than ArmA3, which is built on the very same framework in nearly every way to ArmA2, just with some new features. DayZ is a fundamental rewrite of the engine by the people who made the engine (source). Arma3 uses the same player skeleton as arma2. The changeable cloth is actually model switching, not what dayz has (source).
Oculus Rift Support
100% confirmed for DayZ Standalone. They want to support it – but they need 60fps constant in order to achieve that. That’s hard for any PC title but they’d love to meet that goal (on a high end PC at least) (source).
The MMO Structure
MMO isn’t really a genre “a multiplayer video game which is capable of supporting hundreds or thousands of players simultaneously”. It’s a technical definition. DayZ is an open world survival horror. It was running on what was a military shooter engine. That engine has been modified more in line with MMO technology, allowing large numbers of players to be connected to the same “open world” and be eaten by zombies, and generally betrayed by their fellow humans (source).
The development team has pushed forward much more with entire architectural changes to meet the needs of current functionality, rather than adding “cool new things” (CNS). The CNS can come later next year, the house on the foundation they are build now. DayZ is moving from a FPS architecture to a fully fledged MMO architecture, supporting something like 100-300 players on a server that would currently support 40-50 players. The standalone is going to be better, and bolder, than most people expect. But it is streamlined. It is the foundation for at least another year of CNS (source).
In ArmA3 all updates are sent to all clients. DayZ runs like an MMO, you receive updates that are relevant for objects around you. This cuts down on many issues AND it greatly reduces the impact of hacking. In DayZ standalone, there are many commands which simply don’t EXIST on the client. Like createVehicle. Like setVariable. The client doesn’t even have the ability to conduct these commands. When the client wants to do something, it issues a request to the server and the server does it. This all occurs because DayZ is fundamentally a multiplayer game. It only runs with a dedicated server. ArmA3 is not this (source).
Both Dean Hall and Bohemia would rather make a good DayZ, even if that affects sales. The decision to not release is really very simple, these things take time. They either take the time to redo this MMO architecture or they’ll face a hackfest on launch day (source).