I have an idea about doing a mockumentary

I have an idea about doing a mockumentary, something like This is Spinal Tap (1984) or The Office UK (2001 -2003) a comedy which contains more dry and satirical humor. I have this an idea as it is something I have never attempted before and is something I have been very intrigued in doing for sometime now, the only problem I face is writing a script as even the professional screen writers for such shows and films find it difficult to write something that is humorous but doesn’t deviate from that dry and very British type of humor. This would be similar to the horror trailer except that it would be a fully fleshed out story with narrative and context. Again it would be based off of the films I mentioned in the trailer idea. I am going for a space themed horror film which focuses on themes of isolation and claustrophobia. There would be more focus on psychological scares than jump scares. Mockumentary Horror Trailer A horror trailer would be easier to do as it can be short and it also consists of many different shots which can be quickly cut together. My basis for this is based on trailers such as The Thing (1982), Alien (19790 and Dead Space (2008) which is a game but follows the same themes and context of both of the previously mentioned films, I know I can complete this product to a very high standard and make it look professional. FMP-Ideas Short Horror Film Short War Drama This idea is based off of films such as Saving Private Ryan (1998), Apocalypse Now (1979), Platoon (1986), Full Metal Jacket (1987) and Band of Brothers (2001). I wanted to do something that focused more on the emotion and connection to the character rather than the visuals but there would be scenes of fire fights and intense bloody scenes, it would be mainly set outside as I want to try something that was more guerilla style shooting.