I don't know if extra opinions count but I'd say Jack O'Neill was corect throughout this discussion, both regarding the uniform of the 71st HLI and the 91st/93rd.
Regiments that wore highland uniform and saw service in the Peninsular:
42nd (Royal Highland) Regiment of Foot (post-Napoleonic wars The Black Watch)
74th (Highland) Regiment of Foot
75th (Highland) Regiment of Foot
79th (Cameron Highlanders) Regiment of Foot
91st Regiment of Foot (post-Napoleonic wars the Argyll & Sutherland Highlanders)
92nd Regiment of Foot (post-Napoleonic wars the Gordon Highlanders)
The 42nd sent the 1st and 2nd battalions, the 2nd of which was later disbanded, presumably to keep the 1st up to strength, all the others a single battalion.
That is all.
List of British Army Regts that saw service in the Peninsular 1808-1814:
http://www.napoleon-series.org/military ... nsula.html
P.S. I like the list of foreign units on that page. Seeing 1 or 2 of those in the game would be great.