The cricket board will not mold any players to become aggressive. I think they have the perfect batting line up for Test matches and i am impressed with they way Sri Lanka played in the last two matches and somehow managed to draw the match and both these teams are experimenting with new players and give them some time and we might see good players emerging from these countries as we have seen some good defensive batting from some of the players in both teams.
As far as West Indies is concerned, we can say that they are producing enough young talent. Their major issue is not the lack of talent, but the unavailability of players due to their participation in various franchise T20 leagues abroad. On the other hand, after Lasith Malinga and Kumar Sangakkara retired, Sri Lanka is not able to produce players who have the necessary qualities to replace them. It is understandable, since their player pool is small (as a result of small population). Also, their domestic structure is in bad shape.
It will be interesting times for the lower ranked teams as you say some are having a hard time keeping their players to play for their country because they can earn better money elsewhere. I also think this virus will have an affect on some teams as not many are able to play cricket right now due to the virus and not many are playing domestic cricket so it could put a halt on young talented players coming through.