2 legs for semi of Scottish cup. Finals to be played at Murrayfield unless... both finalists from sames city (then ground decided between them, mediated by SFA if required) or in unlikely event it makes sense to move (such as Hamilton v Airdrie final).
Any neutral stadium for semis in league cup (or even go with a home advantage for the lower placed league team) - the final can be any agreeable stadium.
For internationals... spread the friendlies about far and wide, and let the bigger stadiums bid for qualification matches.
Also, as it seems Aberdeen will move, the SFA should , for strategic purposes, help pay for the move on the guarantee that the capacity will be over 30,000 (meaning the occasional cup final and qualifier can go there as well)