I do something similar in my version of the D&D Multiverse. The Blind Eternities are a stable "layer" of the Far Realm where most of the M:tG sets reside. That's why the Eldrazi and Planeswalkers can travel to all of the M:tG worlds, but not the D&D worlds.I already link the Blind Eternities in my home cosmos. In my cosmos Blind Eternities = Far Realm.
I highly doubt they are going to insert a Magic term into the core.
I just use the Great Wheel as it was in 2e, with the addition of the Feywild and Shadowfell. The Astral Sea can be accessed from the Prime by contacting the surface of a crystal sphere at Spelljamming speeds (i still have crystal spheres), otherwise you have to open the sphere with magic or wait for a naturally occurring opening and end up in the Phlogiston.For 40 years I've had a much simpler system and it works exceedingly well. My Known Universe has evolved with the introduction of some new concepts over the years, but it began with: There is a Prime Material Plane, an Astral Plane, a Positive Energy Plane, a Negative Energy Plane, one Elemental Plane, one Heaven, and one Hell. The Astral Plane was the conduit of travel between the planes for those without Plane Shift or similar magics.
Everything they introduced beyond those in the books, should I have decided to use them, became a region or pocket dimension accessible from one of the above. Most of them are pocket dimensions that you can access easily from the Astral Plane.
As the years advanced I introduced into the mythology that the Far Realms collided with these planes long ago. When it did, it fractured the planes so that transitive planes developed between the Positive and Prime (Feywild), Negative and Prime (Shadowfell) and Far Realms and Prime (Ethereal). By that time I had added hundreds of pocket dimensions and specific regions, including establishing the '9 Planes of Hell' of the Devils existed at the center of Hell and were surrounded by the unlimited regions of the chaotic Abyss. Demons are Devils that were corrupted when the planes collided, and the Blood War is their effort to fight their way to the center of Hell where they can rip open the portal to the Far Realms and see it consume all of the Known Universe.
Spelljammers are used to navigate between planets on the prime, through the skies of the main prime world (or through the Dyson Sphere like interior Underdark), and (most importantly) through the vast Astral Sea. My equivalent of Sigil is found within the Astral Plane and consists of countless portals that were pulled together and lead to various places across the realms, allowing beings to do trade - somewhat safely - across the universes (something highly prized by the dwarven legions that mine the Elemental Planes for resources).
It is far simpler than the exceedingly detailed Greet Wheel or MtG settings. It makes so many storylines easier (the Blood War makes a heck of a lot more sense in my setting), and I have never, for one second, found it to have been problematic in any fashion.
That is similar to how I do it. The Far Realm/BE is actively poisonous to creature of the Aether Realm (the typical D&D cosmos) and vice versa in my cosmology. The more aether a creature has, the more poisonous it is. So gods, composed of massive amounts of aether, find it extremely difficult to pass through the BE (not to mention the potentially dangerous inhabitants there). So though they could use the Far Realm to access Eberron, MtG worlds, etc. (if they know of them) it would be difficult and dangerous and the further the metaphysical distant one would have to travel through the BE, the greater the danger. Additionally, they can't properly perceive the reality of the Far Realm, their normal senses don't function properly and the are essentially blind (thus the "Blind Eternities). This prevents them from easily know what lies on the other side of vast metaphysical distances of the Far Realm.I do something similar in my version of the D&D Multiverse. The Blind Eternities are a stable "layer" of the Far Realm where most of the M:tG sets reside. That's why the Eldrazi and Planeswalkers can travel to all of the M:tG worlds, but not the D&D worlds.
The Far Realm is the only plane of existence that has the ability to connect to every other plane/world in the Multiverse and gets to ignore ordinary restrictions.
Eberron's Xoriat is a small pocket of the Far Realm that got bound to Eberron, and can be used as a "portal" to venture to other settings, but it's basically impossible to survive traveling through it.
So theoretically, you could travel through the Far Realm to any of the M:tG settings, to Eberron, to Athas, and any of the D&D worlds that the Far Realm has taken interest in, but the fact that going to the Far Realm will instantly drive you insane and probably attract the attention of powerful aberrations, this hasn't been discovered in most worlds.