Using a thicker enamel wire and less turns for the primary of the output transformer than the secondary

 At your risk. Any battery must be in series with a transformer for safety.

Today buying from Vangelis Stefos shop in Athens 1mm, and 1.4mm wire. About 200g for some experimentation.

But before this the 1:1 bifilar output transformer will be tried on the Pleiades BD650 power amp but this time operating with just 3 AA 1.2V batteries. So 3.6V and if at 500mA it sounds nice output power should be of the order of 1 watt. In Class A (electrons flowing all the time).

Adjusting bias is very amusing as a sweet point is very easily found by listening. This should take account even subconsciously of the Impedance with respect to Frequency curve of the loudspeaker.