I'd like to present some suggestions pertaining to equipment and research:
Spoilered to shrink down the post.
-Have different tiers of scrap piles that spawn in different areas, giving you better chances of finding superior equipment and supplies in savage or underground areas (e.g.: "ruined military vehicle" with high-tier equipment, "broken ambulance" with medical supplies, "trashed civilian vehicle" with scant (and possibly not that useful) items, etc.)
-Multiple tiers of armor and weapons, each adding additional benefits (e.g.: Tier 2 Combat armor gives additional protection with a helmet that grants EXTRAVISION, Tier 3 adds NO_BREATHE on top of that with more defense. Power Armor could follow a similar progression). When researched, the higher tier equipment can be built, but should be increasingly more expensive with rare components.
-Power Armor, being the most powerful armor, should be extremely hard to find and manufacture (obviously). I had an idea for an 'interface suit', that needed to be worn to unlock the full power of the armor (e.g.: No interface suit = no strength boost). I figure that with an added creature class granted by the suit ( [CE_ADD_TAG:CREATURE_CLASS:INTERFACE]? ) and with the power armor's strength boost depending on that creature class, that might be possible (Absolutely no idea if it actually is, mind you).
-Perhaps some weapons can be researched to help speed tier progression along? Higher tier weapons found on a scrap pile being sacrificed to unlock other technologies, perhaps?