Any portal that returns you to where you entered, or to a single ‘generic’ location solves the ‘free fuel issue’ which isn’t anything to do with people not wanting creative planets to have portal access.
It’s to do with not wanting them used to bypass the travel requirements of the survival universe.
The rest of the issues related to this, as I understand it, are implementation barriers related to implementing a new system for this, or making modificaitons to the existing system.
Honestly, so far my favorite ‘wild idea’ is that creative portals be a different, fixed size unit, as proposed by @majorvex in this post.
@DKPuncherello also made a solid suggestion about a dream realm but that would require implementing a lot more (I think) into the game vs. simply using the sanctum as an entry point.
In every case, there’s a minimum requirement to come up with new stuff - ranging from simply a new way to browse planets in the sanctum to entirely new features or components in game.
Of course I can’t say for sure but it seems like tracking what portal you came in through is going to be a lot less development overhead than many proposed solutions. But Luca has indicated that one of the major obstacles to that is the use of various sized portals.
So that’s why you see proposed solutions revolving more around standardized or fixed portal sizes right now.