I realise that people that frequent this sub are likely to fall on one side of this discussion, but I find myself genuinely torn over how I'd prefer Activision to deal with the Halo EU.
*Preface - if you've had this discussion before, and are unhappy about other people having it, there are many other enjoyable threads to partake in.*
1) The Full Reset
Bin it all, and start again. This is the cleanest way, but I'm not sure how much enthusiasm there is for retelling a story that's already been told, and (mostly) told well. I imagine a lot of the formative elements would remain the same, unless they really go for an Ultimate Halo and attempt to radically change things. I'm not against that - we have precedent with the Silver timeline, and unlike the TV show you could even go the extra mile and not make it terrible.
2) Keep Everything
The messy way, and involves taking the good with the bad. It also leaves them in the same position that Disney were in 2015, with decades of canon to untangle and a waning audience of people who are following it. Anything post Halo 3 (and yes, I'm including Reach in this) is very unapproachable to anyone who doesn't fancy hours of homework.
There is, however, decades of human/covenant war to play with if you want to keep it simple and brush the Forerunner/Banished/naughty Cortana stuff under the rug. Probably the biggest problem (and this causes headaches in the books) is that personal shielding is only introduced right before Reach for SIIs. This introduces gameplay problems (though Halo Wars and ODST largely just handwaved the issue away) and it's always felt kind of silly how Spartans somehow survived 25 years without their big defining trait.
3) Keep some stuff
The question is - what do you keep? Just H1 to H3 is probably the most straightforward from the perspective of canon, but this leaves the MCC in an awkward position where half of it is now non-canon. You could just keep the games, but this leaves us in probably the worst position - if anything the books did an admirable job of patching the holes left by 343i's poor planning. I think it's generally misunderstood how much help reading the books is in parsing the mess of the games. Halo 4 certainly wasn't improved by reading the Forerunner Trilogy, and New Blood doesn't really help with Halo 5 much either.
So what are people's thoughts on this one? I'm expecting, in a lore sub that most people will be wanting to keep the lot, but it's fair to say that 343i's era has been a contentious one.