When you stumble across the Akaviri generals ghost in the viper eye quest, he looks like a reskinned Baurus.

Assuming the invaders were Tsacei, shouldn't he have been a snake-like being?

Beth didn't have the time or resources to model Tsaesci for a one-off quest.

It's hard to say which race it was, but I think we can chalk this up to game mechanics. They aren't going to make whole new meshes and skeletons and things like that just for one ghost character in a side quest.

There's also the skeletons (creatures) in the fort. Though what you say still holds true... they wouldn't make new meshes and stuff just for a few things in a side quest (as cool as it would've been).

It's been speculated that the army at Pale Pass were humans working for (or slave to) the Tsaesci. Considering it was a covert base, and they had people sneaking in and out, it's likely they needed humans so they'd blend in and not draw suspicion (had their been Tsaesci roaming the area, it could've drawn more attention to the fort). Could also be that the snakes don't like the cold temperatures where the fort was located, and so had human servants man the outpost.

Yeah, because they didn't do that before *cough*Yagrum*cough*Udefrykte*cough*Karstaag*cough*Gatekeeper.

It's not even like it was "just a side quest". It was a part of the main quest. Yagrum was just as important in Morrowind's main quest. The Uderfrykte WAS "just a side quest". Karstaag wasn't important in the slightest. He had no real reason to actually be there, but they added him anyway. The Gatekeeper was only a small quest before the main quest was properly in flow. There are actually even more examples, but I'll not get into them.

I put it down to the fact that they didn't want to ruin the mystery of Akavir. Or the more pessimistic view: laziness of vanilla Oblivion.

It wasn't part of the main quest. You only get it after you gain a certain amount of fame. The Countess hires you to do it.

Laziness? Come on. Everyone knows Oblivion's development was plagued with issues. There was very little time to be devoted to content with all the uncertainty and rushed development.

I believe I read a post where MK assured everyone the Teseci's appearance was solely due to the fact they didn't have the resources and tech to do them.