no, reasons:
1) this artifact would most probably take much less space on planet thus no cloak or defense structures etc would be needed = only this one and pure production structures.
2) it is a vital part of this game, that planets can be taken/stolen...
3) we have a max number of invincible planets per player and this would change the number to unlimited (?)
4) IDK, lets mention here also artifact Abysmal Rift Trap
if this would be rather a new extra rare planetary event - natural/random or from Reality Transfuser, that would sound more balanced but still...