@Solarius: I thought purchasing and research were separate because otherwise there'd be no looting advantage? I.e. you loot it, you can now buy it. Otherwise, you could have 'requiresBuy' just reference the item itself and there'd be no research chaining problems.
@psavola: A mission's 'unlockedResearch' is still a single research, how would that be an improvement? By 'auto-completing' repetitive small researched as new mission types pop up? Are there even enough suitable mission types to make it work?
@duendeinexistente: Research chaining can work, but it's a pain to implement without messing up some dependency. You also lose the pop-up reports and have to go hunting in the Ufopedia yourself. Kinda undermines the fun of discovering new guns, but I guess if you already find the current arsenal tedious and uninteresting...

As to UI, I don't think the research UI is that bad. Yes, it could be better, but it does its job - especially now that you can reorder research. Click to research, right-click to ignore, simple. Scientist allocation is the big inconvenience.
IMO, the worst UI in the game is multi-base logistics. Which doesn't exist and you have to do it one base at a time. That, and restocking items you haven't run out of yet. If I remember it right, Starving Poet got so fed up he resorted to writing his own save management tool to get around that when streaming.
Also, those 300 topics are actually 150 topics doubled, and a whole bunch of those can only be done once. I don't think I've ever researched a Magnum instead of Magnum acquisition, for example.
Finally, what's the point of having researchable weapons if the player just ignores the research results? If you don't care about some particular weapon, just hide the research.