If West Midlands is your start point and you're daytripping it, then you're really limited to the southern half of Scotland (south of Edinburgh) IMO - it's quite a drive to get up north of Glasgow where argueably the best scenery starts. So an overnighter in a nice hotel might be a decent plan. I'd guess you don't want to be driving the entire time, so perhaps aiming for a hotel at the furtherest away point (or close to) would be sensible, perhaps Perthshire:
Dunkeld Hilton ain't cheap but the location is stunning, blew me away so much we got married there outdoors.
To get to Dunkeld from Glasgow I'd suggest:
- starting from Stirling, A91 to Yetts 'O Muckhart
- north past Gleneagles on A823
- continue north to Crieff on A822
- after Crieff continue north on A822 directly to Dunkeld
(the above was pretty much the route taken on a z4-forum meet last year)
From Dunkeld:
- east on A923 to Blairgowrie
- north on A93 as far as Braemar (stunning road and scenery)
- and return
Just be aware the weather conditions are making the roads somewhat dodgy at times, but it's changing on a daily basis...