Shockwave, here's my 2 cents on your proposed Scotland mod:
The Scottish special unit:
I love the idea of the Clansman as an early-game unit. The thought of a modified Warrior icon in a kilt, with targe and broadsword, just tickles me.

But a lot of other Civs get their special units around the early middle ages - there's what, two alternate Swordsmen, and like THREE alternate Knights? - so it might be better to go with the Highlander unit and save it for a little later in the game. I'd suggest the following:
Replace Rifleman with Highlander
Rifleman: 4/6/1
Highlander: 8/4/1 (or 7/4/1, if you can get the "treat all squares as roads" mod to work)
This would give the Highlander unit the appropriate offensive punch - the Scots were/are traditionally devastating on the attack - and, in conjunction with the more defensive Infantry unit, would make the Highlander useful for the rest of the game.
Other thoughts:
Scot civ attributes: Militaristic & Scientific, definitely
Preferred Gov: Monarchy
Ruler: Has to be Robert the Bruce. Mary was colorful, but not a good monarch. Besides, she was about as Scottish as Groucho Marx; the Bruce was home-grown.
Cities & Leaders: Calgacus's list is fab! Being roguish, though, I'd like to add Rob Roy MacGregor as a Leader as well...
One last idea: How about giving the Scots the ability to found cities on mountains? If you've ever been to the Highlands, you know that this is appropriate! This could be balanced by increased Shield costs for building improvements and units in such a city.
Keep us posted!