I do indeed have a lighthouse in one of my levels, but it is not drawn on the horizon, it is an object in one of the rooms.
The thing I ran into when trying to make a lenseflare object do its thing (be a lenseflare) was to only make it do the lenseflare thing when the light was rotating towards Lara. Failed miserably... Can't untrigger a lenseflare it seems... And rotating it does not help either: it does not cast the lenseflare in a certain direction.
Anyway, seeing this makes me think something might be possible with a plugin.