I think you misunderstand exactly what a mod for the Creation Engine consists of. The point is, there is no conversion needed. Mods contain absolutely no executable code.
What they consist of are a set of data files in a proprietary format which are read directly by the game. And the game on the console reads exactly the same format files as the game on the PC.
In fact, mods are simply a kind of DLC, with exactly the same data as a DLC, distributed in exactly the same format as a DLC, in exactly the same format on all platforms. If Bethesda ported Fallout 4 to Linux, the game would still read the mod data in the same way as it reads it on Windows or the console kernels.
To be more specific, a mod structure is as follows;
A .ESP file. This contains data which describes the cells, the objects in them, the quests, the NPCs etc.
A .BSA file. This contains assets used by the mod, specifically;
- Meshes of objects and creatures
- Textures for meshes
- Scripts
- Sounds
And a few other things. The only difference between a DLC and a mod is the DLC uses a .ESM file instead of a .ESP file - but those two files are almost identical in structure and content, just a .ESM file is handled by the game with a higher priority.
Getting a mod onto a console, is simply a matter of copying the .ESP and .BSA files into the right place on the hard-drive - the same place as a DLC's .ESM and .BSA. Not something that can be done by the user directly, so what Bethesda have to set up is something in the game launcher that will go to a predetermined site (bethesda.net, I gather), present a view to the user of what mods can be found there, then download the selected mod to the console.
Since Bethesda will control the site that hosts mods for console, they can monitor what gets uploaded there (probably through a submissions process) and reject mods that aren't suitable or take down mods that get complained about.
But the mods themselves won't be converted or ported - they will be exactly the same files, containing the same data, as on PC.