To be fair, OneOne1 almost always have patches and appends that gives more content, though with this new game I highly doubt we'll get more playable characters, at least we know it will be good content (here hoping it's like with Samurai Vandalism and the option to take care of virginity instantly is also added).
That is indeed true, it's definetly a shame that the whole "Multiple Playable Characters" feature might stay lock behind Samurai Vandalism for now, but I think ONEONE1 plans on further developing the other elements of this game to make up for that, all of their games thus far have proven themselves to be evolutions of the other after all
It's probably a tad early for me to speculate this, but so far, I think I've gotten a good idea of how many scenes each character will have when the first vesion of the game drops:
Liz - The MC and sole playable character, will undoubtly have the highest ammount of scenes and CGs, just like all the previous ONEONE1 MC's
Aletta: She is heavily tied to Liz thanks to her not only being Liz's mom, but also her mentor in the storyline, and as confirmed by ONEONE1 in their twitter, she is planned to have a big role in the game's plot and that will include plenty of screentime, so I expect her to have the second highest ammount of scenes, also helps that ONEONE1 themselves has stated that she is one of the most popular characters revealed thus far, probably more so than even Liz, lol
Faith: Given the fact that she is Liz's main rival, I expect her to show up fairly often in the storyline of the game and to have a fair ammount of scenes dedicated, though definetly nothing compared to Liz's family
Camilla: I honestly have no clue on Camilla, mainly because she is the character we know the least about thus far, no CGs, no animations, no nothing, we only know that she is Liz's childhood friend and that's about it, which leads me to believe she might just be the one with the least ammount of scenes dedicated to her, of the main cast anyway
Sitri: I would say the same goes for Sitri, specially since we know even less about her than both Faith and Camilla when it comes to her role in the story, but at the very least she HAS had one of her scenes revealed, which leads me to believe she will have more scenes than Camilla, but probably less than Faith
Roxanne & Stina: These two are only side characters, so I fully expect them to get the treatment most side girls in ONEONE1 Games get of having a grand total of two scenes and nothing else, maybe even less so if ONEONE1 puts more focus on the main girls this time around
This is all just speculation of course, a lot might change between now and when the game actually comes out