One Issue we continuously have is when and why to use a SQL based derived table, or an explore based derived table. We have opted to use more SQL based derived tables as we often have unavoidable long chains of cascading DTs due to the complexity of the platform we are reporting on. These cascading explore based DTs become very hard to debug and keep clean code when combined with intermediary explores that rename the dimensions combining multiple other DTs from other explores.
Often we want to extend our views like classes in other languages and add extra joins so that we can have different things for different more specialized purposes without losing base behavior objects. LookML does have some extending and class inheritance behavior, but it does not have super capabilities. Currently, you can only completely overwrite properties from the extended object. It would be incredibly useful if it were possible to instead add on to the property like in other languages. This would really help in the possibility of building reusable code, clean code.