EASY LAYOUT 4S LITHIUM BATTERY CHARGING MODULE

Hi to all!

I'm building an almost "in-line" UPS, in the sense that in the absence of line voltage the load immediately takes power from the batteries without having "shortcomings".

I know that there are specific chips to act as a charger, regulator and BMS for batteries but my request is different and I cannot use a chip already made and I will explain why.

The lithium batteries (in my case 4S) would be constantly and always under charge and in order not to deteriorate their life I thought of keeping their maximum charge at 16.8V (4.2V x 4) or even if possible at 16.7V (4.175V x 4), to create a circuit to balance them and overload protection.
So I thought of using the chip to regulate the output voltage from 24V to 16.8V which goes to the BMS I made "ad hoc" which protects the batteries, and also via the Rlim limits the charging current of the batteries to 300mA , so that the first charge is long and slow and then the power "lost" in the balancing circuit is quite low (300mA allows me to recharge the batteries to 100% for the first time after many hours, but slow charging makes good for the batteries without stressing them and also once they are all charged to avoid over-charging the current will pass through the 47ohm 1W R resistor and will be dissipated).
Obviously there will be a microcontroller with which I will read the current (which since the batteries are in 4S series will be the same for all), the temperature and the 4 voltages of the individual batteries and show them to me on a display so that if there are problems or anomalies the microcontroller will drive a mosfet which will immediately disconnect the entire circuit, sending it into protection.

What can I use?
I perhaps saw that a product like the LT1510 could be right for me (even better if in the SO-8 configuration which would take up less space on the board but I haven't understood if that's what I need.
As components I would prefer them to be easy to solder (SO, SOIC, HTSSOP, perhaps avoiding QFN or other).

To summarize, I would like to impose a maximum voltage of 16.8 V (and once reached the batteries will stop charging) and a current limit of 300 mA.
During balancing, 300mA will be "lost" on the 47ohm resistors, while once balancing is achieved the current supplied will be practically zero and the DC-DC will continue to convert the 16.8V to keep the batteries charged which will be protected by the designed BMS ad hoc composed of:
- INA226 ADC (for current and voltage readings)
- DB18S20 temperature sensors
- HY2213-BB3A balancing module

In normal conditions the 24V line will go to the load, if the 24V home line ceases, then the batteries will have to come into play providing their 16.8V.

Do you have suggestions?
Thank you all.