In regards to buying terrain and Bastions:
I have never really been a fan of 'buying terrain' as part of a list and have usually been in favour of scenarios to handle this type of thing. I will note however that probably my most memorable game was 3000 points of Black Templars in a Fortified castle holding off 6000 points of Iron Warriors for 4 turns before transports arrived (much like the scene in Starship Troopers). Pic below:

My vision for the list is not so much a force that carries along it's own Bastion or castle, but rather a force that arrives at a destination and finds itself under attack shortly after by an opposing force. When doing this, the Imp Fists (known for their ability at defence and fortification) make use of what they have at their disposal and set up for the coming battle. As they are supposed to be superior at this, the following things do make sense to me for the force:
- Fortifications
- Razor Wire
- Mines (I am going to look at these now)
- Tank traps (as 'mines' above)
- Gun Emplacements
- Tarantulas
- Bunkers - this was a small stretch however the book Sons of Dorn did have them using melta guns to fortify positions and there is no reason why established bunkers or improvised ones are not out of the realm of their skills in such a short time.
All the above represent a case of "dammit, we do not have immediate support and we are against the numbers but we will show these curs that it will not be so easy to take this area".
Now I am all for scenarios to shake things up. I am making this list up for the GT however, so anything larger than the fortifications and bunkers is really not what I am looking for. If there did happen to be a Bastion set up on my table edge however, I would pity the force having to assault it

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Also on another point that has come up - the change over for short ranged items such as the dreads to be replaced as well as the standard Land Raider. A siege is just as much about hitting the enemy from afar, as well as restricting access for them to access certain key locations. I am not in favour of reducing the whole force to 15cm and 30cm shots and relying purely on assaults to decide the battle. Hence I will be looking at a balance when considering options. Some of these are as follows:
- I have the LR Crusader in at the moment. While it is there, the LR Redeemer has no alternate role to play in the list and the standard Land Raider fulfills the need for longer ranged AT weaponry
- Dreadnoughts: I am still looking at these, however having 2 CC dreads makes no sense to me at an Epic level. They both fulfill similar roles. It is all part of the micro-detail that I would rather stay away from. A Siege dread could be either the Ironclad or the Siege - In effect the stats are not so different that either could be modelled on the stats presented. What I do take into account is, as you have pointed out, other lists may wish to use Siege or Ironclad, so I will go about separating the two listed under the one line as requested.
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I hope the above clarifies rather than confuses my outlook on this project. I know I am not going to please everyone, but I will do my best to gain concensus
