Not a problem, army lists should be sent to me first but will not be rejected out of hand if they are not 'official'.
However, I was intending to play-test the scenarios as something completely different and 'non-competitive', and will need everyone to be 'sensitive' when playing them. I have tried several and they play very differently to the usual tournament game. As such they are both very refreshing and challenging - but they are also a work in progress. There are still some unclear points that will need to be discussed and played through. This does not mean that 'un-official' armies won't work, but it would be helpfull if they were more 'average' than 'power-gamed' or 'extreme'. (so 13 THawks and a Landing Craft will not be allowed OK)

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I would also add the some scenarios will favour one style of army over another. This is one reason why I want to exclude 'Hold at any cost', because 'Nids and especially Siegemasters (and their fortifications) are at a huge advantage if defending while at a huge disadvantage if attacking (the same is also true to a lesser extent in 'last stand'). Depending on preferences we may just concentrate on three or four of the scenarios.
Finally as noted above, it may be sensible to prepare two army lists that may be used if you are the "attacker" or "Defender". This is because some scenarios and roles require a lot more mobility than others - making the game much less enjoyable if you have completely the wrong army make-up to start with.