I have two:
1. "Daggerfall 2", mentioned above.
My interest in this title, however, isn't related to the game's backstory or specific mechanics. What got me so excited when Arena and especially Daggerfall first came out was the thought that they heralded a new direction for CRPGs. I loved the concept behind combining a wide array of procedural systems/simulations, and then layering custom content on top of that procedurally-derived simulation.
I envisioned how great the games could be if CRPGs continued down that evolutionary line, being built upon progressively more robust, more realistic, and more interesting systems for procedurally generating geography, climate and weather (with an impact on the game), civilization patterns with varying population densities and trade routes, intercity and international economies and relationships (including wars and truces), various types of dungeons and other man-made or natural enclosures, calendar events with an impact on the game (seasons, full moon, equinoxes, etc.) and quests. This stage would then be used as the setting for custom created content to drive "the main story".
The only games that really derived their approaches under this evolutionary chain (in some respects, at least) were the Roguelikes (which I know preceded Daggerfall, but mostly lacked the custom content and storyline overlay), the Diablos (and I'm not at all a fan of their combat system) and now Dwarf Fortress.
I really would have liked to have seen more commercial games evolve from that basis. Sure, Daggerfall's particular implementation of some of their systems wasn't ideal. The dungeon generation system, in particular, comes to mind. But as an early generation attempt at that technique for developing a CRPG, it was very cool. Imagine how robust dungeon generation systems could be today if they'd gone through as many generations of refining their algorithms and options as they've gone through on graphical engine upgrades.
I also really loved that Daggerfall was one of the few RPGs that offered "push" quests instead of exclusively "pull" ones, and the fact that they were often timed and failable. Most heroic fiction (that CRPGs are in some ways intended to reflect) is better served by that approach. Cardboard NPCs that stand around waiting for the protagonist to arrive and ask them if they need help with anything is just not representative of the underlying fiction, and is dull. It's much more exciting and engaging when someone seeks you out for help, or the antagonist starts taking dangerous action, and you have a limited amount of time to resolve the issue.
2. The other game that I would have liked to have had more spiritual successors was Starflight. In particular for this game, I'd combine my love of the old Elite-style games (Freelancer, Privateer, et al.) where you customize, upgrade and configure a spaceship that is usable for free-roaming open-ended activities such as trade, piracy, anti-piracy, running missions, and mining with my love of traditional turn-based, six-or-so member party RPG mechanics.
I'd start with an Etrian Odyssey styled game (more or less a modernized and refined clone of the early Wizardries that incorporates a great in-game mapping technique...it also has lame anime graphics, which I would not incorporate). Then I'd add some deeper combat mechanics (Wizardry 8 and Wizardry:Tales of the Forsaken Land both offered some interesting ideas for adding additional richness to the traditional six-man blob combat style). I'd use blasters and vibroblades instead of bows and swords, of course.
The party members would be recruitable crew members (medical officer, pilot, gunnery officer, etc), with some banter and personality. The crew members, however, would be there for flavor and not be the focus of the game (think halfway between the original Mechwarrior and Planescape:Torment).
This half of the game would be used when at space stations, planetside, when boarding other ships, etc. The Elite-style element would come into play when in your ship.
Random missions, custom side missions, and main quest missions could take place either fully in space, fully on the ground, or using a combination of both.
The RPG stat system would have dual skill trees, allowing you to decide how you want to balance their predominantly space-based and ground-based skills.