Would it be possible to have a mod that lets you visit the Braithwaite Manor in the prologue?(Or after the mission: Blood Feuds, Ancient and Modern) I don't know what can be made possible but if there is a talented modder out there looking for a challenge why not this one? 😉
 

I dont use any trainers, but I suppose there is one which allows you to clip through objects? With clipping you can get through any locked door.