As long as the extra repeaters are LED and draw no more current than the OE option that should work fine. I'm sure you could do away with one plug/socket set each side on your splitter to repeater though. Also remember green/white wire is right and green/red is left indicator circuit.
Note there is no CANBUS lamp monitoring but the flasher unit is designed for LED indicators only. The repeaters draw a miniscule amount of extra current.
FWIW when adding a loud bleeper to indicators on my Roadster I just cut into loom and added double female bullet connectors on each indicator circuit to provide the necessary extra feeds.
