Feel this is worth sharing here: Stuart MacLennan's example of what Scottish STV constituencies might look like: http://www.stuartmaclennan.co.uk/2016/05/what-would-scotlands-political-landscape-look-like-under-stv/ , which I think have been drawn pretty well given the difficulties.
I'll be honest, I never get why people are so enthralled by STV, especially given one of the most frequently made criticisms of MMP is that it isn't proportional enough. STV is somewhat proportional, but a) it's only somewhat proportional within the constituency, not nationwide and b) for good proportionality it requires constituencies that elect a large number of members.
For example, look at Ireland, which only uses 3-5 member constituencies, FG and FF always get many more seats in the parliament than their vote share would entitle them to (excluding 2011), and in every election small parties that get 5-10% of the vote are lucky to get more than 3 or 4 seats, when under an actually proportional system they would be expected to get 10-20. Given that the biggest problem with Scottish Parliament elections has been that the first and second largest parties are always overrepresented and the other parties are underrepresented, STV will only make that worse.
This can also be seen in McLennan's STV examples, which also use 3-5 member constituencies. In his predictions the Greens would only win four MSPs (down 2), and the thing that's most telling is in Edinburgh, they wouldn't win a seat in the Central or North constituencies (where there are a higher concentration of Green voters, but only 4 seat constituencies) but in the West and Pentlands constituency, because it has 5 seats, and therefore a lower quota to get elected.
STV also has the disadvantages that only a tiny proportion of people who voted for the Greens are represented by a Green MSP, whereas currently Green voters across more than two thirds of Scotland have a Green MSP they can contact. And, yes, a lot of these problem can be solved if you made the constituencies larger, but (keeping the Scottish Parliament the same size as it is) setting a minimum size of 8 would require constituencies half the size of current Scottish Regions, which would pretty much destroy any local representation.
Finally, I get that people say you can redistribute your preferences how you want, full control of your own vote etc., but I don't think that STV is that perfect in practice. I remember during last Irish elections one Labour TD was elected by complete surprise because he edged ahead of his opponent in the penultimate round after, by his own admission, receiving a last round batch of 10th, 11th and 12th preference votes for him. I know that that's how STV works, but I can't accept those results as a deliberate decision by the electorate to say we want this candidate over this one, given that he received many fewer high preferences than his opponent, rather than just the results of STV sometimes being completely random.
TL;DR With 3-5 member constituencies they don't solve any of the problems with MMP, create new ones; with constituencies of 6+ it'll destroy too much local representation; a better way would be to look at how you could improve the existing electoral system (Sainte-Legue, open lists, larger regions, others) before saying we need to switch to a new system.