As far as lag goes, the simulator itself is what is lagging, my CPU runs it under 6%. The game needs to take more advantage of more powerful CUPs when they are available.
This type of program is not meant to be run on any old computer, every try running autocad on a $200 computer?
Yes, the dev of this type of program will take a very long time.
Note: I do not claim to be a good programmer in this area, as I am just starting to learn xml and stuff (having previously learned lsl), but I would be very planning and making the graphical part of the GUI =D.
Try to not have the point of view that this is impossible, bad idea or hard, instead think: This is what needs to be done, how it will be done and maybe start a long term project.
If you're on windows, it will likely BSoD, Linux will just slow down, and if you leave it finish simulating, ...a fridge with hot food and explosives in it, it will finish in ~2 years