In the cases on which the complexity of the analog circuit increase significantly, it can be useful to split the simulation into different environments otherwise will take too long, namely the logic part in Proteus (firmware) and analog part of the LTspice, but for most cases Proteus pretty suffice. Another option is to change analog models by replacing them simplest primitives.
You can say that about all simulation programs. Some though will allow you to add some models, which may be an easy or complicated procedure. Proteus has one of the most complete model libraries out there.