A new version should appear. Not only must it solve the tented vias problem and the decoupling problem, but also gain a bit of room for the added capacitors.
There is one area with little usage near the brightness potentiometer. But it's far from the 3.2V rail. Another solution is to switch the 74HC04 package from SOIC to SSOP. I got some TC74VHC04FS but they are rated at 5V, I'll have to see how they behave when undervolted at 3.2V...
OK, don't buy a part before looking at a datasheet, kids !
In my case, I was lucky and it says :
- High noise immunity: V NIH = V NIL = 28% V CC (min)
- Wide operating voltage range: V CC (opr) = 2 V to 5.5 V
I shoud probably add a bit of hysteresis...