I have the answer. I joined the forum precisely to answer this problem as I've been a proponent of revamping the system greatly ever since I joined OBD. Here's how I think we should imagine Multiverses, or spaces larger than Universes in general.
Let's start with a basic example. Take 2 0-dimensional objects, points basically. It is easy to see that 2 points are separated by (or in this case, connected by) a straight line, a 1-dimensional structure.
Now take two parallel lines, 1-dimensional structures. They are separated by a 2-D plane (or, more appropriately, lie on a 2-D plane) of whatever size.
Take two 2-D planes/sheets, and they're separated by a 3-dimensional space/cuboid/whatever.
and so on. You can extend this logic to any number of dimensions (in fact, we prove this in my Linear Algebra classes).
Similarly, if we imagine a normal universe to be a 4-dimensional continuum (3 spatial dimensions and 1 temporal dimension), then 2 universes co-existing in a verse, would in fact be separated by a 5-dimensional "hyperspace" or as I call it, a barrier, as that is the logical consequence for this line of reasoning. This reasoning isn't perfect by any means as it treats temporal and spatial dimensions as the same but it is a much better and more nuanced system than what we have currently, it's also flexible with room for changes/improvement.
And this coincidentally fits well with most fiction. Since DB plays an important part in this conversation, I'll use its example. Conveniently, DB has perfect examples to illustrate this fact. If we recall DBS: Broly movie, Broly and Gogeta clashing their fists seems to "break" reality and sends them to a weird dimensions that is referred to as the "Dimension of Swirling Lights". This dimension is hard to explain but in essence, the guys who made the movie intended for it to be a literal higher mathematical dimension and
this post explains it extremely well. What I'm getting at is that the DoSL is one of these "higher dimensional" spaces that separates the Living Universe from the other realms such as the Otherworld, Kaioshin realm, etc.
Another great example in DBS comes from the U6 tournament arc. The 12-18 universes in Dragon Ball are stated to be separated by a separate realm/dimension called the Neutral Zone. This neutral zone is stated to exist
between the universes, and in a DBS guidebook (I'll find the scan if needed) it is stated to be a separate dimension by itself and is compared to the World of Void and Zenos's realm, both of which are also separate dimensions themselves. This serves as a perfect example to illustrate this. The dimension is also quite large, containing countless galaxies as well as Super Shenron who himself dwarfed multiple galaxies.
I've given here a basic outline of how we should revamp the existing system. My next posts, which I'll get to soon, will be addressing the other two big issues. The first would be destroying 2 universes vs one infinite universe. And the second would be addressing tiers above Multiversal+/Infinite Multiversal.