As most of you know, Stephen Loftus is the guy who did the size comparisons of things in the Halo universe. Well, when I emailed him about when we may see an update to that project, this is what he had to say:
Hi, thanks for the email!
I would love to do an update for newer Halo 5 objects. The unfortunate thing right now is I don’t have the Halo 5 CG models as I do for almost all of the other objects in my scale charts. That’s how those charts are made. Only a few exceptions are hand drawn by me such as the Fleet Battles ships and the Halo Wars vehicles.
In the case of Halo Wars vehicles, I was able to do those based on having screenshots that were provided to me of the CG models that I could draw from. I had those screens from work I’d done with 343 Industries on the first Visual Guide book. I was able to add some Halo 4 content when I worked on the Halo 4 Visual Guide, but as you know, there was no Halo 5 guide book and I don’t have either models or screenshots of the side views of those vehicles and weapons. I really wish I did!
As it is now, there may be a few more items I can add such as the Halberd-class destroyer, and some of the things you mentioned below like the Guardian, Acrisius,
Installation 04 control, Installation 05 control,Installation 00 citadel and control center, possibly Halo Wars Forerunner ship. The greater Halo rings and Greater Ark should be possible too.
<em>As to Threshold, Substance, I can put the in the black and white scale chart I guess, but I’d already done some scale work on them here (http://halo.bungie.org/misc/sloftus_planetscale/images/HaloPlanets2.jpg) and here: (http://halo.bungie.org/misc/sloftus_planetscale/images/Haloverse-PlanetDistances_scaled.jpg) so I just didn’t think to include them in my regular scale chart, but if you think they would be good reference to have all in on place I’d be up to including them.</em>
I’ll see if I can include some of what I’ve discussed here in the next update. I do hope the reminder of what I can’t do becomes possible. Believe me, I want to see this stuff as much as you do!
Thanks for your interest in the scale charts! Very glad to hear from folks who find them useful or entertaining. 
Stephen L.
If you haven’t seen the project yet, head over to
http://halo.bungie.org/misc/sloftus_scalecomparison/