I came up with some thoughts for a mod like this some time ago, and actually began work on one with a friend of mine, but I ran out of time to work on the mod after starting law school and my friend has been working on several cool projects of his own, and is unable to finish work on this one. As a result, I wanted to throw this out there for anyone looking to create a lore-friendly mod that has not been done before, and that in my opinion is well-needed.

I've always believed that Orvas Dren is a very powerful character, not necessarily in raw power but in influence, minions, wealth, etc. Nevertheless, I've found the quest options where you have to kill/gain his support to be pathetically easy, and uninteresting, with the possible exception of the "blackmail" route. The goal of this mod was to make the process (especially the combat route) more interesting, and to add a bit of death to an otherwise dry quest.

The goal of this mod was to increase the difficulty/depth of all three ways in which the player could deal with Orvas Dren. In addition, is was to add on the Dren Plantation, creating a small system of caverns underneath where the player could find an alternative route into the manner, gain a possible companion for backup support in the fight against Dren (a disobedient slave he had imprisoned), and weaken some of Dren's backup support before facing him. Some of the things my friend and I thought of are posted below.

-Expand the size of Dren's villa to make it more fitting for one of the richest men on Vvardenfell
-Make both the Ienith Brothers (if alive) appear behind you to attack whenever Dren enters combat
-Put several bodyguards with powerfully-enchanted crossbow bolts and a mage inside the front entrance of the mansion (and a trapped carpet similar to the one used in a Bloodmoon quest) to make an uninvited front entrance extremely difficult.
-No one simply walks into Dren's Villa (which will require a key for entrance). Instead, the guard by the door asks you to break a Camonna Tong member out of jail, and to return him safely to Dren Manor in order to enter peacefully. As an alternative, you could kill the guard and take the key, but then you'd have to deal with everyone in/on the plantation except slaves turning hostile.
-Alternatively sneak in through a series of smuggler's caverns beneath the mansion.
-Increase the power of all the Camonna Tong at the mansion, and add 1-2 extra ones by Dren himself (always felt Dren deserved a big orc goon with a warhammer).
-Create a distraction to sneak into the smugglers caverns by slipping a potion into the netchs' food that makes them go crazy and attack the guards.
-the blackmail letter is now a lot harder to find, and you now have to set up insurance (i.e. making copies of the letter and asking someone to reveal them if you die) in order to confront Dren with it. Otherwise he'll just laugh and kill you.
-One of the people on Dren Plantaion is also a member of the thieves guild if viewed in the CS. Perhaps a thieves guild plant? If so, he helps you find a way into the villa
-Persuading Dren to work with you requires that you kill the judge in Ebonheart (same one Fighters guild quests asks you to), Percuis Mercius, Gentleman Jim Stacey, and the Dagoth residing in his caverns.
-If you've killed Sjoring Hard-Heart, are a member of the thieves guild, or completed Larrius Varo's quest, Dren refuses to work with you. You'll have to blackmail him or kill him.
-Dren has (when you confront him in the vanilla game) made a deal with the sixth house. If you sneak into his caverns or confront him personally, this is now apparent (a "Sixth House Emissary" is at Dren's side and a Dagoth is residing in the caverns).
-The caverns (should you choose to sneak into them) contain traps disarmable only if you have sufficient sneak.
-Dren himself is increased in level and abilities, and his spear is enchanted

The dialogue that you wrote for this mod was really good.