hi
for the battery holders i had a idea some time ago. the battery holders of the bigscale FG cars might fit very well as holders on a e maxx chassis (gmaxx, FLM etc). there are to sizes. long (about 23cm) and a shorter one (around 19cm). they might be shortened if needed. the fg part number is 05014/6 (short) and 05014/7(long). they are from durable plastic.
a colleague of mine tried it with the shorter ones on a gmaxx chassis and his first response was very positive.
just as a suggestion.
bye
rhylsadar
here you see a pic. in the middle.
click