nn.Sequential containers can be used for simple feed forward models, where the layers are just connected sequentially and pass a single output to the next layer.
Often models are more complicated than this approach and cannot be easily mapped to nn.Sequential, which also seems to be the case here.
Based on the error message I assume that a particular layer outputs an OrderedDict, which is then processed in the original forward method and creates the error in your approach.
To remove some layers I would thus recommend to replace them directly with your new layers using the layer name:
model.layer = MyLayers()

or if you want to disable them assign an nn.Identity() module to the corresponding attribute.