Allies and Fortifications

Allies have become a very important part of 40k at larger points values. However at 600 points they are much less common and more limiting. As mentioned in the previous post the force organisation chart can be very limiting due to the mandatory nature of some units. Adding allies to this just increases the amount of things that you have to purchase.

However saying that, allies can still work for some armies (especially those with cheap troops). You can easily fit in a Eldar Farseer and some bikes into a Tau army to provide psychic support (and even offence) to the otherwise markerlight reliant Tau as well as some fast troops.

Fortifications however would be much easier to fit into the points limit. However I admit that I have not had much experience at all with fortifications and so the following will just be reasoned assumptions. 

Cheap durable buildings such as the imperial bunker could be incredibly useful. They would allow a unit to hide in relative safety, and due to fire points be able to provide some decent supporting fire (eg. Imperial guard heavy weapon teams).

The only other real fortification of note would be a void shield generator. Many armies would struggle to strip the shields and it could give you a turn or two of immunity from fire. However I have not tried these and so could be wrong.