As a returning player with a small nation, I will offer what I have experinced returning.
First thing I had within 2days of joining was a war was declared on me(non-alliance). For me I am lucky that I have experience to deal with this. A new player with no experience would struggle and would likely be put rapidly off the game. During this time I joined an Alliance, was sent 6mil/4k troops. This boosted my NS range up and allowed a larger nation in the War to declare on me. At this point I had a couple of improvements. The nation that declared had full military improvements and a couple of wonders.
This instantly had me in a position where options are limited. The alliance I am in pumped aid and troops into my nation. This had no real benefit, if anything it made the problem worse. As it allowed the attacking nation to take more from my nation during GA. In the end I did a $30 donation to put me in a position to stand a chance.
From the above my recommendations would be:
Nations under 1 week cant be declared on. This will give new players a chance to get in an alliance and assistance.
Aid time needs cutting down to 5 days, this means smaller nations can get more aid, as their warchests are smaller and will rapidly deplete - your not going to easily fix the problem with nations with more improvements and wonders, it will always be something to deal with during war.
Other than that, I personally dont think there is much that can be done to rebalance things to help a new nation.