- Core rules without Heroic Fantasy - fix various flaws and loopholes, add improvements from Axioms
I guess this is the default assumption about what a second edition of ACKS would be: Not a new game, but the core game we all know and love, only with the rough edges that've been discovered in the years since its initial release smoothed over, the holes in the rules filled in, and a fresh lick of paint.
This sounds like it would be great for people who (like me) are already running ACKS campaigns by the book and don't want to change much, but would welcome some slight tweaks that improve rule clarity, fix up the more awkward mechanics, and give us a few more options without taking anything away. On the other hand, I imagine it might not be the most useful book you could release; since the changes are likely to be small, people who are already running ACKS campaigns might not feel that the new version is really needed. I guess it's hard to predict which of those would be the bigger group.
- Revised core rules re-built around Heroic Fantasy
Ah, so basically Heroic Fantasy, but written as a standalone game rather than as a set of modifications and additions to the core rules.
That sounds like it would be great for people who (like me) yearn to run heroic fantasy because it's awesome and does a great job of capturing all the tropes of the heroic fantasy genre, but are reluctant to do so because it means having to juggle and adjudicate a two sets of rules that interact and override each other in complex and occasionally tricky-to-remember ways. Also, the need to juggle two sets of rules makes the learning curve steeper for players and GMs who aren't already familiar with ACKS, and a version of ACKS with the Heroic Fantasy changes baked in to the core game would solve that.
On the other hand, Heroic Fantasy already exists, and is still fairly new; a new second edition probably wouldn't introduce many changes that aren't already in the existing heroic fantasy handbook, so again, this wouldn't necessarily introduce much in the way of content that GMs and players feel they need.
- Completely new game built around Heroic Fantasy, perhaps adapt it to feel a bit more like 5E (attack bonuses instead of attack throws or whatever)
I'm not sure what you mean by "completely new game." Are we talking about throwing out all of ACK's existing mechanics and starting from the ground up by making an entirely new game deisgned to support heroic fantasy plots rather than the "first you adventure, then you conquer a realm, then you reign and defend your throne against all comers" progression that ACKS is built around? Or do you mean to keep that progression from ACKS, but substantially redesign all the mechanics from the ground up, abandoning some of the proud nails of OD&D in favour of D&D 5e's... Uh... Actually, I don't know a lot about 5e, but I assume it has features which people like, and which are superior in some respect or another to the way OD&D did certain things.
I guess that'd please the 5e fans. Me, I'd have to see what the changes actually were before I could make up my mind. I really like ACK's focus on hexcrawl logistics and realm management and detailed economy and internally-consistent setting justification for everything beneath the winged sun, to the point where I tend to adapt them in some small measure whenever I run anything else... So, I'd be a little hesitant to play a game that deliberately distanced itself from those things. On the other hand, if you made a game that still included those things, it'd also need some improvement or new feature that made it significantly superior to ACKS, or there wouldn't be any point in making the switch.
Then again, "customers want what they know," and all that. Perhaps if you made something completely different to ACKS as it currently stands, I'd rapidly realise I wanted it.
At the end of the day, I'm likely to back nearly any kickstarter project Autarch announces, so my views probably aren't the most important one to take into account when making this decision.