Just my opinion, but if you manage the WD right, they don't need anything else to make them more extreme. They at upper levels after feeding a lot can:
1. Damage isn't DRASTICALLY far off from the SOVEREIGN, I bet if the game lasted long enough, they will eventually outpace the Sovereign.
2. Hull strength can easily get over 10,000, I've seen over 15,000. Probably could reach 20,000 if the game lasts long enough.
3. It can repair ITSELF at an EXTREMELY rapid rate. So over 10,000 hull and can repair itself when it's surrounded by enemies!! DO NOT underestimate the shear absolute ability of this to tip a battle in your favor, although it does require micromanaging the WD to make sure it uses it's powers correctly.