How about drawing power from Social Links?
To elaborate, it's one thing if a guy fights to "protect everybody". It's another thing if this same guy fights to protect somebody personally. It's one thing if a guy swings his fist to "end the fight". It's another thing if he puts purpose behind his fist. Interacting with people - properly interacting with them - leaves an impression on both sides. Sure, in digital stories and forums/comments/chats discussing them, many possible motivations and purposes can be brought up. But seeing an actual person who does something despite of, or does something because of; seeing, how and why a person makes their decisions makes their motivations and purposes actually alive.
It's not a concept I'd gotten to yet, but it is one worth thinking about.
Masahiro, for example, initially fights because Kanako guilts him into it and then because it provides an escape ("If only
all my problems were so handily solved with a boot to someone's face..."), and only gaining heroic motivations later on.
Kanako, once she's able to, fights partially out of an acknowledgement that "it's the right thing to do", but moreso because she detests the way these scientific creations - the Psychroids - are being used (in her eyes) irresponsibly/to harm people.
Gen fights the Emotion Monsters
and Masahiro and Kanako largely because he believes it's dangerously irresponsible for
anyone to even
posess that kind of power independently of government oversight, and to a lesser extent, because once he gets to know Masahiro and Kanako personally, he believes that the two of them
specifically shouldn't have the power they do. "Terrible role models like you should never be thought of as heroes!"
As far as the original point about Social Links go, I haven't really thought a whole lot about how Pathos' powers will develop over the course of the story yet, and that's an interesting concept.
Writing this comment, I have realized two things. First, I have no idea what "old-school" and "new school" Kamen Riders are supposed to be. So I'm probably replying to a question you haven't asked. Second, I need to spend more time with IRL friends.
When I said "old-school", I was referring primarily to the Showa Era Riders (70s, 80s, and 90s), wherein the heroes were almost universally cyborgs who rebelled and fought against the secret evil organizations that kidnapped and roboticised them (SHOCKER and derivatives).
Up until Black RX (early- to mid-90s, and the last Showa-era Rider to have a full TV series), none of the Riders had any of the form-changing or toyetic gadgets/collectible powerup items you see all over the place nowadays. And even RX only had two alternate forms. (as opposed to the way Heisei Riders like Kuuga and Wizard have a myriad of different forms with corresponding Elemental Powers)
Usually, the Showa Riders just had their own smarts/guts, their cyborg enhancements (which, outside of transforming into Kamen Rider, you basically never saw onscreen), their Cool Bike, and that was pretty much it.
Then, in
Kamen Rider Ryuki, (got an epic PR-style adaptation in the US as
Kamen Rider Dragon Knight), each Rider had additional powers/weapons they could invoke by using a card. And then the device the card was inserted into would call out the effect. "ADVENT" for summoning your contracted monster for a super move, "FINAL VENT" for your Finishing Move, "SWORD VENT" for summoning your weapon, etc.
These kinds of tropes usually remained in the shows that followed, but got a little tamer as time went on, and AFAIK only showed up in the shows that actually used cards (which would be
Blade, and then
Decade).
Hibiki, in a bit of a one-off thing that would later become huge about five shows later, also introduced the idea of having tiny, handheld transforming robots (often animal-shaped) that could act as information-gatherers on the heroes' behalf.
And then
Kamen Rider Double hit, and the merchandising aspect of the franchise went freaking
insane. Where before, only a handful of Riders transformed with the use of a collectible gimmick (the aforementioned card-using Riders), now
anything that could hypothetically be mass-produced for collectability became an integral part of the transformation device - often with varying powers as well. Double used USB sticks to gain elemental powers, OOO used a combination of three Medals (coins) to gain animal powers (with a much more powerful elemental form if he used a full combo of same-color Medals), Fourze used plug-n-play switches to adapt his tools and powerset like a Swiss Army Knife, Wizard used magical Rings to change forms or to invoke spells, Gaim gained could change his arsenal of weapons and armor
with freaking LOCKS, Drive got new powers pretty much by equipping Hot Wheels....
Etc., etc.
Kuuga and
Agito, the first two shows of the Heisei Era (the two immediately preceeding
Ryuki) are a bit of an in-between phase, in that both of those Riders have multiple forms with elemental powers (although downplayed in comparison to many later examples like Double and Wizard), that was an inherent part of their powers, and they didn't need any kind of additional trinket besides their original belt to access them.
Agito, also, was I think the first show to really popularize having more than just one Kamen Rider per series. It (along with some of the other mid-Heisei-era shows like
Faiz and
Kabuto) are probably my main inspirations for
Pathos.
