under VMC, the combination of the 2 airports would not be a problem. Alverca would be a tight visual right hand for 04 and Lisbon departures can make the immediate left turn to LIS
... However, the margin is extremely thin.
On instruments... Landing on Alverca04 at 5NM and 1500ft, would bring you to within 1NM of the Lisbon departures. It would be very hard to ensure a minimum of 3NM separation... let alone targetting 5NM.
Alverca22 & Lisbon21 gives less problems if the Alverca22 SIDs call for an immediate left turn.
Ideally, Lisbon 17/35 should be the one used for landings with about 2200m...
If Alverca is to be used intensively, Perhaps:
Lisbon 35Dep/03Arr, Alverca Dep/Arr04
Lisbon 21Dep/17Dep, Alverca Dep/Arr22
Problems for the long hauler departing 03... or those requiring landing 21.
Now the question arises... where would the long haul departures be? Lisbon or Alverca? Alverca should be extendable to 3800m... Unless the space to the south west of the airport has been developed...
Montijo's current 2450m runway 08 can be extended.. if you want 3800m, well some residents have to be displaced.. Extending 01 to the north will involve reclamation and can bring the length up to 3600m-ish... but I dunno how deep the water is. The bridge from the current airport to the Montijo area can be used... but, unless you make the 01/19, you're gonna make the other airports in a bit of a conflict... So, if U're gonna use Montijo, scrap the other airports.