What is the subject of 其他的都很满意?
I am glad to see this interesting question. The omission is really one of the most confusing but fascinating parts of the Chinese language. My explanation would be almost similar to your first one.
There are two omissions in this example. One is the omission of the subject. The other is the omission of the verb.
除了价格以外，（我）（对）其他的都（感觉）很满意。
Except for the price, I feel very satisfied with every other thing.

除了...以外 - except for
价格 - price
我 - I
对...感觉 - feel
其他的都 - every other thing
很满意 - very satisfied