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So I have done this great exercise where you alter one note at a time to create a new chord:
Cmaj7 C E G B
C7 C E G B♭
Cm7 C E♭ G B♭
Cm7♭5 C E♭ G♭ B♭
Cdim7 C E♭ G♭ B♭♭
This really helps you visualize how chords are made, so I wonder what other chords can you start with to do the exact same exercise?
Don't forget about the basic triads! But in order for your particular system to work, you'll have to start with either the augmented or diminished triad:
+ C E G♯
M C E G
m C E♭ G
° C E♭ G♭
Also, note that, with one small adjustment, you can string some of these together to just keep going through all chordal roots. As one example:
Cmaj7 C E G B
C7 C E G B♭
Cm7 C E♭ G B♭
Cm7♭5 C E♭ G♭ B♭
Cdim7 C E♭ G♭ B♭♭
Cm7♭5 C E♭ G♭ B♭ (return here to keep the one-half-step rule)
C♭maj7 C♭ E♭ G♭ B♭ (enharmonic to Bmaj7)
B7 B D♯ F♯ A
Bm7 B D F♯ A
Bm7♭5 B D F A
Bdim7 B D F A♭
Bm7♭5 B D F A (return here)
B♭maj7 B♭ D F A
And so on.
Otherwise, it seems you could do this half-step exercise with pretty much every extended tertian chord (9ths and above), since you can always explain something as, e.g., ♯11 or ♭13 or add9.
I've also taken the liberty of editing your Cdim7 to use B♭♭ instead of A. In short, since that pitch is the seventh of the chord, we want to spell it as the note a seventh above C. Since a seventh above C is B, we want to spell that pitch as some type of B—in this case, B♭♭—even though it's enharmonic to A. When we spell it as A, we actually create an Adim7, since the thirds of A C E♭ G♭ stack with A as the root.
Here's an example with 9 chords.
What about something like this?
C E G (C major, of course) B E G (E minor, inverted) B D G (G major, inverted) B D F# (B minor)
... and so on.
This sort of thing might help you compose, because you will know which chords are really close together, if the passage requires something like that.
One common contrapuntal technique is to take a chord like C-E-G and change to a C-E-A; it's called the 5-6 technique by some authors. (Bach liked this technique apparently.) Obvious other examples are just taking C-E-G and making C-Eb-G (thence to C-Eb-Ab creating movement down four flats by only making two chromatic tone changes.)
