vs Ostheer, you do not want to go lieutenant due to the fact mortars are very possible since they are in the same building as grens and thus your MGs will not perform as well. Lieutenant is fine against OKW since the lieg is not really a strong counter to MGs. Captain is always a safe bet for the at and Stuart. If you like using light vehicles you are going to need push for fuel.
After thinking about it some more, my final answer is Captain.
1. RE Bazookas is not ideal for Rifle company with the RE Flamethrowers (might as well make them full anti infantry). So you are going to have to rely on AT guns more.
2. You are probably wanting to rush easy eights, so usually if you go into Lieutenant usually you go for captain after wards.
3. White phosphorous and Pack Howitzers could be a great combo.
I hope this helps.
Yes it does thanks