Houston's core in 2017 (fWAR in parentheses):
Keuchel (2.5) age 29
McCullers (3.0) 23
Altuve (7.5) 27
Correa (5.2) 22
Bregman (3.8) 23
Springer (4.5) 27
These are the core players on the Astros. The ones they can count on year-in year-out for 3+ wins. Might not happen every year, but based upon track record this is what can be expected. And some of them obviously contributed much more than 3 wins.
To supplement this core group, they added high quality veterans like McCann, Verlander, Beltran, Reddick, Gattis. I don't have Marwin Gonzalez in the core group because arguably 2017 represented a career year that was well outside the range you could have predicted form past performance. It doesn't hurt to have someone step up like that.
For comparison I list below the six guys who I think will be our core players by 2020. Obviously there is uncertainty and we can debate the list. My six are:
Freeman age 30 in 2020
Inciarte 29
Albies 23
Acuna 22
Gohara 23
Soroka 22
If we want to think about filling the holes, we would want high quality veterans in left, at third and at catcher. Maybe a pitcher too. Even without a boost to payroll, there should be some flexibility to add those kinds of players, considering that Albies, Acuna, Gohara and Soroka will all still be pre-arb in 2020.
I know someone will chime in that it is silly to compare us in 2020 to the Astros in 2017. A lot of things could potentially go wrong. But I think the raw material might be there.