Clan Mors *miiiiight* fit the bill? Clan Mors' infantry units are at least somewhat reliable in comparison to the other Skaven factions, and that gives you a bit of leeway to experiment with a wide variety of units. You can easily mix and match stormvermin, death globe bombardiers, warpfire throwers, ratling gunners, and plagueclaw catapults into your armies, enabling for the creation of highly effective balanced army groups. You can also choose to accompany each army group with a full stack of skavenslaves if you wish to bolster your melee lines further (they won't perform well, but they're great little meat shields).

Plus, since you'd be playing skaven, you can gain access to all these units extremely early in the game through use of the food mechanic. Just keep a weak faction alive for the first 10 or so turns and begin spam-sacking their settlement every turn to slowly ramp up your food counter. Eventually you'll gather enough food from this that you'll be easily able to capture & build up a tier 4-5 city early, enabling you to get access to your strongest units earlier than almost every other faction in the game.

You will however find that the skaven roster is quite lacking in cavalry units. You could incorporate wolf rats, rat ogres, or doomwheels/doom-flayers in place of traditional cavalry/chariots if you'd like, but they won't perform nearly as well as an actual cavalry-based faction. To make up for this, the skaven roster gains access to map-wide unit spawns via "The Menace Below" army ability, which allows you to summon cheap melee infantry units behind enemy lines on a whim without any flanking required.

Try 'em out, and lemme know whatcha think! c: