Although it is legal for drivers to work to rule, I don't think it is legal for the union to encourage or recommend it without a ballot, action short of a strike would cover it, maybe someone who knows more about the law could confirm this.
I drive for LUL, I started a a guard, These are my feelings on the safest way to dispatch trains in order of safety.
1) Guard monitoring platform with platform based CCTV and monitors on train, as train departs, with access to an emergency brake.
2) Driver monitoring CCTV as train leaves the platform, (as happens on some stocks on LUL), There are issues here for drivers which are more serious than on LUL. Mainly the much stricter SPAD policy for Network rail drivers. Start up againsts did increase on LUL and this is a much more serious issue for a driver if three spads mean goodbye career. There is also a greater risk of staff being on the track on network rail, obviously in tunnels there should never be anyone on or around the track. There is also the advantage of being able to leave a platform slowly and knowing if someone is doing something stupid as you depart.
3) Guard dispatching as currently happens, not particularly safe as anything can happen once the doors are closed and nobody is watching, even platform staff, if present, do not have the ability to stop the train in case of indecent.
4) DOO with train based monitors which switch off as train departs, this has all the disadvantages of both 2 and 3
5) DOO with platform based monitors/mirrors, images tend to be worse than with train mounted equipment and more prone to being affected by sunlight, again all the disadvantages of points 2 and three
On LUL instructions are that if, as a driver, you are unhappy with visibility you must get assistance and if no one is immediately available then you wait. In any case you do not ever "Self Dispatch" from a curved platform where not all doors are visible from the cab.
One thing I am sure ASLEF will be doing (and will have been doing before this dispute was even thought of), is to advising all drivers not to depart without following correct procedures and I strongly advise all drivers to follow these instructions both because of the current dispute and because of legal cases we all know about.
Please note that this post is purely about train dispatch, there are many other guards duties which imo are far more important than dispatch.