Pseudo shift usually results in one or more parts of the body to become animalistic but not the entire body. A full shift would be full blown wolf for example, a pseudo shift could be just ears or just tail, or just claws, or just the muscular structure, or just fur (great for if it's cold) or rearrange the bone structure to make four legged running easier and faster.
Also any required mind/instincty thing? I personally am thinking have the normal mindset be rather direct and cold but the shifted mindset be effectively a puppy on a sugarhigh. Be rather amusing.
Pseudo shifts would, indeed, be possible. However, werecreatures would not be able to take advantage of this unless they were to have animagus training. Because you are trying to connect with an inner animal that is not naturally a part of you, your own natural inner animal gets, in a fashion, jealous. Because the werecreature in question has not attempted to get into contact with their natural inner animal and is instead trying to seek out a foreigner, the natural animal gets catty and proceeds to fight it out with the wereanimal in order to get attention thus causing the werecreature much spiritual/mental pain and suffering. Coincidentally, this is also the reason why werecreatures have moon sickness.
The mental and instinctual aspects of werecreatures are also somewhat affected by the wereanimal even when they are not shifted. As such, unless said werecreature got Death sealed into when the werecreature were a baby, it would be very improbable for the werecreature to maintain its cold and direct animal unless they were able to complete their animagus transformation in order to counterbalance the wereanimal's influence via connecting with their own inner animal.