Some others will be able to get preggers, not most.
Currently the player is only preg in gameovers, but like mentioned before, there will be scenes where the player won't be in a gameover and preggers for a scene.
People can commission to put their character in the game yes. If the character is owned by someone else, then as long the owner is ok with their character being in the game it's fine. Making up a character that you just want to see is fine as well.
Prices vary based on what you want, but if those who are curious can contact me via patreon or discord to talk more about it.