So I have a problem with my Grey Knights.....a Land Raider problem

So I have 4 Land Raiders...and I think I have 2 more to build (Phobos and Redeemer)...Or had

While on my 19 day Honeymoon in the UK/ Ireland, one of the many stops was in Warhammer World and I left with this kit....

While the rules don't exist for these or if Grey Knights have these....Mine will. I will make them more Grey Knight looking, hopefully. 

Then while on ebay I found a kit I have wanted for a while and is long OOP.

Land Raider Prometheus Command Tank, once again no rules but  once again.....no rules but I still will use it.  

When these will be built and painted I have no clue.