I am happy when players actually hide the Ovoid-- too many new players are afraid to hide it and then combat gives the strongest player the easy win in the end. In my opinion, a player who spends time hiding the Ovoid and finding the Displacer deserves the win if the other players were unable to deduce where the Ovoid is. Make sure you play with Landing Flags after a game or two so it isn't too easy to hide the Ovoid and have everyone lose complete track of it.
I agree that the Temporal Displacer is the primary threat to someone hiding the Ovoid until the final turn. It makes you go "pick up" the Ovoid close to the end. Some groups don't like the possibility that a player could Displace without possessing the Ovoid, but I would recommend to those players that they always play with Vlachlos so the threat to hiding the Ovoid is that Vlachlos could Displace.
Strategy wise, the last player has an easier time because they retrieve the Ovoid using hyperspace on the last turn of the game leaving no other players to react.
However, if a player goes first when they retrieve the ovoid they have to sustain all the other players making a last effort attack.
Therefore on the last turn of the game if a player wants to use a hyperspace token, they need to roll a dice, if they roll higher than their player number or a hyperspace token they cannot use their hyperspace token and must preform something different on their turn. Eggs always succeed for this roll.
The variant work in that players stop relying on the last turn hyperspace. Although I am not convinced it fixes the balance, but instead shifts it a little. I'd be glad to hear thoughts.