A little gem from Ben Lesnick last night in the chat roll.
(http://i.imgur.com/ErRMHP3.jpg)
So it seems you'll still be able to pick up that ship that you like at a later date, albeit without LTI. Everything except the Idris-M and the Scythe. (I interpreted Ben's double negative as you'd be able to get the Idris-P).
Sneaky, it looks like your wish to have an Idris on day 1 might come true after all!
Idris Briefing Room:
(https://robertsspaceindustries.com/media/3r8132wfcyb47r/post_section_header/Idris_briefing_room02tex.jpg)
(http://img1.wikia.nocookie.net/__cb20130629044346/starcitizen/images/a/a2/IDRISdownfrontquarter-Copy.jpg)