I think the BUKs only change the center of the ship. The frames retain their various armor, agility, etc. So the Sentinel has horrid armor but greater stealth and agility.
On the Hornet comparison, I agree the Sentinel is too fragile. That needs to be fixed. Hornets are one-shotting Sentinels, which should be impossible. Keep in mind though, for a fair comparison the Vanguard needs a REO. That brings the turret to the game which flown right is a serious advantage, and makes the missiles much more ready. A REO should change the balance of power. S3 guns in the turret should make it much easier to convince players to sit second seat.
And, if the electronic wizardry of the Sentinel ever comes to game, there may be an argument for a third player aboard. If they put a mini-game into the fancy console, to use it and the turret in battle will require a third player. While I’m all for overloading players with things to do, they can’t be in both rear seats at once.
In Star Wars Fantasy Flight Games TTRPG, there’s an elaborate “slicing” role that is computer invasion during combat. That would be extremely cool for the Sentinel. CIG has never said exactly what the Command and Control function will be, nor the signature spoofing they sold us. One can only guess if they’ll ever live up to those words.
Finally, one wonders what CIG plans to do about the superior missile lock time on the Vanguards. That also never came to pass. Given the Rattler’s very close missile lock ability, knocking lock time from 0.8s to 0.4s would be a huge boon, especially if they made the switch from turret guns to missiles instantaneous. That would keep the REO entertained. If the third seat was constantly switching from spoofing, signature slicing and power management, all three players would stay busy in combat.
