It would be incredibly easy, like so easy.
The thing is, I'm actually sure he's already bi or pan, because in the comics he doesn't seem to have actual preferences. There's the famous "I didn't say I wanted a woman, Clint" panel (though there's more to that than most people think, but that's a story for another time).
And the fact Namor invited him to a threesome, telling Steve to "celebrate the freedom you profess to love so much" aka in this context freedom of sex and sexuality.
(Namor is from Atlantis, by the way. His thing is that he has a love-hate relationship with humanity, except for Steve who he seems to steadily respect and like).
And I've talked about it a lot before, but Batroc the Leaper and Steve most definitely share sexual attraction to one another.
Batroc has already openly admitted it, stating he thinks what he and Steve share is as passionate as lovers, and Steve has showed fondness and trust towards Batroc despite being enemies. In one issue, Steve only had a few hours left to live, and he chose to spend them all talking with Batroc over tea.
Then in the MCU there's his closeness to Bucky, the trust and lingering looks, the fondness, they share something deep and close. You can see them as brothers or best friends, but I've always thought the jump to lovers wouldn't be so big.
There's Sam, who was pretty much his non-confirmed love interest in TWS. Sam fits all the requirements Steve's listed (shared life experience) and makes him happy, makes him smile. They immediately take to one another, trust each other, support each other.
In Avengers Assemble: Black Panther's Quest, Steve shares great trust and fondness with T'Challa, and the two are very close throughout the season, sharing more than a few moments.
And then there's the fact he's very often put in kind of sexual-ish positions that make me wonder as well, you know?
There's also tons, and I mean literal tons of comic covers where he's tied up in some kind of way.
All in all, to me personally Steve is either bi or pan period.
He loves everyone, no exceptions💕