Can you use the rules for replacing asteroids with huge ships in a tournament?

My buddy and I tried using them for the first time and it really changes the game up dramatically.

When there is FFG prize support involved, from what I understand, they are not supposed to be used for competitive play. Ultimately it's up to your TO to allow them or disallow them though.

I'm not aware of any specific ruling on this, but it appears that they are not legal for sanctioned tournaments (regionals, nationals). But I believe huge ships are always referred to in the context of the Epic format, so that would exclude them from non-Epic tournaments even as obstacles. Locally, TOs can do just about anything within reason.

I'm organizing local store tournaments and may add huge ship obstacles once we run through the goodies from the prize kits.

I'm thinking that I'll put the Corvette at table 1 (where the highest-ranked players play after the first round), the Transport at table 2 (the next lowest-ranked players), and will randomly assign that big planet token that comes with Attack Wing (the only thing from that game that's of any use in X-Wing) to some other table. These obstacles will be optional, counting as a player's three asteroid placements, but will otherwise be treated exactly like asteroids for the purposes of placement (the player with initiative can choose to place an asteroid or a huge obstacle as their first placement).

I would not say this changes the game that much. I played one and it just meant we played near it and it did not change the game.

As for the tournament set up. Its not in the tournament rules (I don't believe) so I would say no. As its nothing something thing everyone one has. Everyone has rocks as they have the starter set.

that would exclude them from non-Epic tournaments even as obstacles.

The rules in the rulebook state using them as obstacles in standard play. It has clear rules for standard play, just nothing out there about tournaments.