Wrapping an association with a specialization of the buildin `Set` (=) function?

Question

I want to wrap some association data into a dedicated symbol (S by example)

S /: S[a_Association][k_] := a[k]
S /: Format[s_S] := 
 "Demo, here are my keys " <> ToString[Keys[First[s]]]

I use such approach (but AFAIK this is a common one) as I see two benefits:

1/ easy argument filtering

foo[S[a_Association]]:="Hello S!"

2/ syntaxic & looks sugar:0

s = S[<|"A" -> 1, "B" -> 2|>]
s["A"]

prints:

"Demo, here are my keys {A, B}"
1

However when you have a nice syntax for s["A"], you also want a nice syntax for s["A"]=3. This is even mandatory, as

s["A"]=3

is misleading/bug prone:

It does not change the internal association:

s // First    

<|"A" -> 1, "B" -> 2|>

but only binds 3 to s["A"]:

s["A"]

3

So far my solution to the problem is to modify the buildin Set function as follows:

Unprotect[Set]
Set[s_Symbol[k_], v_] /; MatchQ[Hold[s] /. OwnValues[s], Hold[_S]] := 
 Block[{a = First[s]}, a[k] = v; Set[s, S[a]]]
Protect[Set]

Now

s["A"]=3
s["C"]=4
s // First

prints

"Demo, here are my keys {A, B}"
"Demo, here are my keys {A, B, C}"
<|"A" -> 3, "B" -> 2, "C" -> 4|>

as expected.

My question:

Before using this in "real" developments, I would like your advices:

• is this approach ok (no side effect,...) ?

• is there a better approach/solution ?