We could assign probabilities to cards that fate egg could hatch into.
a simple example:
40% Mid range beatstick (stone golem, graviton merc, etc)
25% weak beatstick (ash eater, dragonfly, etc)
20% Dragon or strong beatstick
5% non-Time creature with activated ability
5% Time creature with activated ability
1% animated weapon
1% Chimera
1% fate egg (lol)
1% upgraded fate egg(for unupped version), or instant win 300/300 creature or something (for upgraded version)
1% as above, but opponent gains control