The job I mentioned was for several PC market related things. One of them was to develop and implement their own PC PSN store strategy, a separate point was the strategy for Steam and Epic. And more related stuff like growth, sales, partners, etc
Obviously the PC store won't be made by one guy. They already have a huge PSN team, and also a team that develop apps or OS stuff as could be the recent PSN phone app, or the emulators etc. They also had another job offer to work on emulators.
If they are smart, they'd reuse their PSN store website page and phone app simply adding PC as another platform there, as it already had PS4, PS5 or Vita. And then they could do some non-invasive optional launcher, or even to skip it including the trophies in-game and use the phone app for friends/user management and use Discord for messaging/void chat.
They already have a huge infrastructure that can reuse in a big part, more than a lot of work to develop stuff to new store I'd say it's more a strategy thing of deciding when it's the right moment to release it, pricing, 3rd party stuff, make some market research for all these things (another thing mentioned in the job offer was to research about user needs), decide how to exactly implement the stuff, to investigate the best way to fit it in their strategy and so on.