It should be easy to add u32 and array of bits for modbus read functions.
Just create the memory (hal_malloc) in mb2hal_hal.c -> create_each_mb_tx_hal_pins,
then create the hal pins (like hal_pin_float_newf) in mb2hal_hal.c -> create_each_mb_tx_hal_pins,
then decode in mb2hal_modbus.c -> fnct_04_read_input_registers and fnct_03_read_holding_registers
The problem is free time to code and test