I have a similar circuit on my bike. Rather than using the NE555 and two 6v relays, I use a 6v LED turn signal flasher designed for a motorcycle. It is a little pricier option ($21.50 on eBay) but simpler. I also use off the shelf 6v multi-LED automotive turn signal, tail and brake light bulbs (Superbrightled). Again, simpler but probably more expensive. I’m using dual element LED bulbs on the front for turn signal/running lights. I like your arrangement and may try something like it in the future.
One thing you can do to simplify the circuit is to remove the 24 ohm resistor from the charging circuit. The coil that the white wire hooks up to has a couple ohms resistance on it’s own. Additional resistance is not needed, especially with an 8ah battery. I use a 1.3ah 6v lead acid battery. I ran tests with and without a zener regulator. Either way, it never overcharged the battery. An 8ah lead acid battery can easily burn off the entire output of the white wire with no harm. If you are worried about overcharging the battery, the zener would be a better option. Additional resistance wastes charging power before the battery is fully charged. The zener regulator won’t waste anything until the battery is full. In my experience, neither is needed with the HT white wire/rectifier diode.