After a long time, several prototypes, a few hundred sales of previous variants, i think this is one of the two best forms for this kind of product.
Unfortunately, i cannot fully test either of the two versions completely because i am still missing parts for both (expecting replacement for a lost package) .... I couldnt resist though and had to test what i could.
Top is MultiFA-S
Input 5-40V2.4A max
Charger 1S-1A max
Power Path (DC UPS function)
I2C Fuel gauge
2 intependent outputs
A. 5V1.6A (cont.)
B. 3.3V0.8mA max
It is designed in RPi Zero format and can be used for one as a DC UPS but can also be used on its own for anything else plus, there is a matching logic board (same size/format board with atmega328pb, rtc, its own buck/boost for battery power and available IO and an OLED)
Bottom is MultiFA-L
Input is 5-28V4A max
Charger 1S Li-Ion/LiPO 2A max
Power path
I2C fuel gauge
Output here is a simple boost converter in SEPIC configuration so its adjustable from 0.6-24V (5V1A-12V0.25A) which can also be configured as a versatile LED driver for led with forward voltage from as low as a couple volts and up to 24V and with current from 20-500mA (can go higher).
This is also in RPi Zero size but not intended to be used with one...
It is though possible to use with the same logic board.
Test results are frankly as expected, i am very pleased and i hope they sell well too...
I am considering the possibility of a crowd-funding for them so i can reduce their cost and make a lot more than i plan but that is consideration.... perhaps if i get enough encouraging comments i do just that

In this photo, Model S on top is charging while Model L is driving a 500mW led (with 100mA so i can take a photo !!)
Further testing gives aprox 77% efficiency driving a 12V6W led (with aprox 2.4W though, didnt want to take it further as its already too difficult load for it!)