Well, what I can tell you is that Lucy and Tanja will never ever interact with each other. That doesn't mean that other household members won't know about her, just that Tanja and Lucy will never meet each other again.
Not yet, but I promise to give the weebs a lot of love in 0.19!
But it would be wierd if MC marries all the girls (including Tanja and Lucy)and they would not interact at some point in the game(perhaps after a big timeskip of some kind),it wold actually be very interesting to see how MC would be there to help them slowly get used to each toher and/or constantly spend time with both of them until eather of them starts to speak to the other and guide conversation from there until Lucy will forgive Tanja and can at least tolerate her presence or even become firends with Tanja 2.0 with saying something like("Tanja that tormented you in the past is long since dead and this Tanja is a completely diferent person that have many things in comon with you Lucy,she helps people with their problems whenever she can")
Also would be good to improve sex scene's becouse quite a few updates already they are almost stale(same poses,cant actually see penetration,cant see dick and pussy until after sex,small variation in camera angles,very little movement of body parts beside what we have already saw many times,etc)it would actually be interesting to see kissing during sex,that MC would grab the girls by the Ass/Tits/Head and Kiss/some movement of his hands on the girls body,same for the girls,in other words the more variation the better,aside from that the game is one of the best i have ever played on this site,in my Personal Rating its almost on the same level as WVM only slightly lower becouse WVM has bigger diversity in sex scenes and characters seem more alive(more diferent movement variations and not only on the sex scences)