The thing with the Piececlopedia is that the articles are primarily supposed to be about the pieces, not the names — so a page about “the Lancer” isn't really well‐defined in the sense you mean.
Some of the ‘Lancer’s you mentioned do have some history of their own: you've noted that the Lancers Chess turning piece has uses in a few games (albeit all by the same author); the (4,2) leaper, though rare due to its severe binding, has been used by problemists (as the Stag), as well as in a couple of games by Charles Gilman (as the Charolais); the Wild Jokers piece is more commonly known as an Alibaba, which already has a page; TigerChess' lancers are also well‐attested (most commonly as Modern Dabbaba/Elephant) though without pages; and the Pawn Shōgi and Starbound Sliders pieces are (apparently one‐off) enhancements of Shōgi's Lance. It might also be noted that there was a proposal to rename Betza's Fibnif (which also has a page) to ‘Lancer’
Of those that don't have pages already, the ‘Modern’ 2‐square leapers and the (4,2) probably deserve articles, assuming anyone is up for writing them; the one from Lancers Chess might as well (it's an interesting piece and the only one herewhich doesn't exist under any other name) but the fact that only one person has used it might disqualify it (though standards have varied in the past)
As for Falcons, George Duke's piece has seen enough use (not to mention an independent reïnvention) that it probably deserves a page; the fBbR Hunter counterpart (a.k.a. Hawker) might do too though a comprhensive overview is probably more difficult as it's very easily independently devised
The thing with the Piececlopedia is that the articles are primarily supposed to be about the pieces, not the names — so a page about “the Lancer” isn't really well‐defined in the sense you mean.
Some of the ‘Lancer’s you mentioned do have some history of their own: you've noted that the Lancers Chess turning piece has uses in a few games (albeit all by the same author); the (4,2) leaper, though rare due to its severe binding, has been used by problemists (as the Stag), as well as in a couple of games by Charles Gilman (as the Charolais); the Wild Jokers piece is more commonly known as an Alibaba, which already has a page; TigerChess' lancers are also well‐attested (most commonly as Modern Dabbaba/Elephant) though without pages; and the Pawn Shōgi and Starbound Sliders pieces are (apparently one‐off) enhancements of Shōgi's Lance. It might also be noted that there was a proposal to rename Betza's Fibnif (which also has a page) to ‘Lancer’
Of those that don't have pages already, the ‘Modern’ 2‐square leapers and the (4,2) probably deserve articles, assuming anyone is up for writing them; the one from Lancers Chess might as well (it's an interesting piece and the only one herewhich doesn't exist under any other name) but the fact that only one person has used it might disqualify it (though standards have varied in the past)
As for Falcons, George Duke's piece has seen enough use (not to mention an independent reïnvention) that it probably deserves a page; the fBbR Hunter counterpart (a.k.a. Hawker) might do too though a comprhensive overview is probably more difficult as it's very easily independently devised