For now:
1. OGSF (upgrade to 5G)
2. WM (upgrade to newest technology)
3. LM (upgrade to 5G)
4. DRS (upgrade to 4G or 5G)
5. ESS (upgrade to 4G or 5G)
6. AOD (upgrade to 4G)
7. AYPG (upgrade to 5G)
8. AYPW (upgrade to 5G)
9. BIATBWS (upgrade to 5G)
EDIT: Added BIATBWS to the list. Could be also an interesting one.
1. OGSF (upgrade to 5G)
2. WM (upgrade to newest technology)
3. LM (upgrade to 5G)
4. DRS (upgrade to 4G or 5G)
5. ESS (upgrade to 4G or 5G)
6. AOD (upgrade to 4G)
7. AYPG (upgrade to 5G)
8. AYPW (upgrade to 5G)
9. BIATBWS (upgrade to 5G)
EDIT: Added BIATBWS to the list. Could be also an interesting one.