The glaring omission which I see is you are only going to the Glasgow and Edinburgh central belt and the Highlands and will miss the whole of the rolling scenery, historic castles and fortified towerhouses, battlegrounds etc. of the south of Scotland, the rolling Southern Upland hills with their moorland and forestry, the Scottish Borders Abbeys, and the Solway Coast of Dumfries and Galloway.
However there is only so much you can see in the available time and you will at least catch fleeting glimpses of southern Scotland as you travel by train from Glasgow or Edinburgh to London. The train journey on the west coast route from Glasgow takes slightly longer than the east coast route from Edinburgh but is more scenic, at least where it passes through southern Scotland and northern England.