As a guy who knows his obscure lore, I can tell you, that, yes, to some extent, guns exist in TES lore. Professor Numinatus had an arquebus that shot good ideas.
Except Build Your Own Home already does that. At any rate, I'll reserve judgement on Hearthfire until it's out. Bethesda usually tends to implement things into the game better than modders, except in some cases.
According to the admins, they are planning for the mod manager to support Morrowind, as well as splitting TESNexus into separate Morrowind and Oblivion sites.
It's not just about searching for mods. In general Oblivion mods get preferential treatment here, and a lot of Morrowind modders get their work confused with Oblivion mods.