Vuelo, whilst connecting into a hub (which many slate BA for doing incidentally) is a good thing, TAP doing a 4 weekly service does practically sod all for connections and would become primarily O&D. If you are saying LIS needs TAP and MAD needs IB because you would rather see a legacy carrier then just say it. Theres no shame in it.
In the meantime if Easyjet were to offer MAD it's something that we couldn't turn our nose up at. The route would/should do perfectly well with just O&D and despite IB's Latin American strength, existing carriers can still serve those markets. Remember that IB's South American strengths are by far based on it's own O&D attributes.
As for EZY MAN-MAD. It would be great to see MAD back on MAN's departure boards. However simply splitting MAN/LPL-MAD wouldn't work unless there was some kind of frequency enhancement. i.e existing mid day/early aft from LPL supplemented by a morning and evening service from MAN. Otherwise an whole sale move of the route would be the best option.