Big Post Time!
Thoughts on normal SM list: First question: where are things standing in regard to the Army Book? Hena collected up everyone's lists and made some changes to the standard list - is that stuff still going forward, or are you compiling it all again?
In general, I agree with E&C, GlynG, Signal, MikeT, etc. Looking at the most current version of the Marine list (completely ignoring changes made for the Army Book, since I'm tired and don't want to look them up):
Unit stats:
The Captain: One option would be to replace him wholesale with the Supreme Commander. Another option might be giving him reinforced armor (to represent the presence of an Apothecary, his own artificer armor, and his Iron Halo). One could give him Scout or Infiltrators, to represent the associated veterans. Sniper, to represent his superior precision.
The problem is that any improvement to him logically follows through to the Supreme Commander, and the SC's just fine. Of course, the SC is mostly taken for his reroll, I think. So improving his CC ability wouldn't actually make him that much more desirable.
The Predator DestructorFirst, it should be FF3+. It's got at least as much firepower as a Devastator squad, and can concentrate it better - FF has always seemed to represent quantity of firepower as much as anything else. IIRC, a poll a while ago got pretty good support for at least testing such a change.
The problems with the Predator formation stem at least in part from the fact that the Destructor simply isn't worth as much as the Annihilator - fixing that will make it easier to balance the formation. Adding Librarians might happen, but we can always just pretend they're Techmarines.

Disparities with the Russ can be explained through superior Space Marine technology and training.
RazorbacksEither the HB Razorback should get +1FF, or the LC Razorback should get -1FF.
SpaceshipsPersonally, I'd like it if the spaceships had slightly larger transport capacities - right now you can't squeeze in a Dreadnought with your Battle Company. The Strike Cruiser is also short a BP (2WB = 1BP, 1BC = 1BP, going by the Battle Barge).
I think it also might be worth considering giving Space Marines some pin-point attacks (1 for the Strike Cruiser and 2 for the BB, maybe?). While I could understand some reluctance, the list is very weak in that area and it's a large part of the popularity of Warhounds, as I understand it.
Regarding upgrades: Why does the Attack Bike option even exist? The formation could be "any combination of Bikes and Attack Bikes" and the change would be precisely none. And it would be one less upgrade.
No Razorbacks for Scouts. They need transports, and adding the Storm would be cumbersome (IMO), but giving them the Chapter's best Rhino-based transports doesn't make much sense either.
In regard to restricting aircraft: I did it, and I think it was the right move for the Apocrypha. However, it's not necessarily compelled for the main list.
Comparing your proposed cost changes: Tacs to 275 - fine. Sensible, even.
LR optional upgrade - fine to some extent, though I would point out that Tacs don't usually run around in Land Raiders. With, perhaps. But not IN.
Predator optional upgrade - A, you'll need to make one. B, that's a rather large change for the basic list.
LRs at 300, 75 - I'd support the second. I'm not sure about the first - 325 might be better.
Vindicators - I don't know that they're
that bad. If you give them Walker, I think they'd be worth 225. Not common as dirt, but a reasonable choice.
Dreads to 25 with 4+ - I like the 4+, but I don't know that I like 25 each.
Thunderhawks to 250 - speaking as someone who actually did this - do 225. 250 is likely excessive (for all that the variants are apparently worth that, and they can't do Air Assaults like the base version...)
Warhound - 300 each is overkill. 275 plus the critical is good for the moment - if they're still common as dirt, that will be noticed.
Scouts to 175 - Yes. But do NOT remove the Rhinos.
Predators - they need something. Especially if you cut Land Raiders to 300.
Overall, I'd have to say it's too much too quickly. Not that you shouldn't make some changes, but this is a lot. I'd say drop Tacs, LRs, Preds, and Vindicators by 25 points and increase Scouts and Thunderhawks by 25, at a maximum. Even that'd be a lot for one update to a core list.
Thoughts on Apocrypha: Generally, I want to leave the list alone for a while and let it mellow. Whatever version gets published IS going to be publicly left alone for at least six months.
That said, I've got a variety of changes I'm thinking about (including the name, since many people don't seem to get the reference and my chapter-with-a-suitable-name is almost done). For example, I left the Predator cost at 275 because going lower seemed too radical. Now EUK's down at 225 and I feel all square and old-fashioned (and also like I was right all along, but that's another issue

).

Many of the proposals for the SM list, if accepted, would make the AoS even less distinct, and I'd need to deal with that. Plus, the costs would be all out of whack compared to the base list - indeed, a lot of the costs are as they are because the base list was where it was and Hena was already of the opinion that the list was just "basic list plus more stuff that's cheaper".
Furthermore, looking at the list, I'm not happy with some of the compromises I made and can think of better ways to deal with them. Plus, there's some stuff I could cut without appreciably affecting the list's feel, and so I suspect I probably should if I get the chance.
Points of contention include the concept of the list, the inclusion of both old and new stuff, and the inclusion of Tarantulas in any form other than completely immobile gun batteries. Oh, and whether to go cheaper or keep costs closer to the main list.