I think the paddle steamer Waverley would make an interesting addition to the line up ...
http://www.btinternet.com/~Paddlers/PSWaverley/
Yes, it would also be great to have her fleet mates PS Kingswear Castle and (the ex Red Funnel ferry) Balmoral included too...
http://www.waverleyandbalmoral.co.uk/balmoral/articles07/rye/index.htm
Waverley in particular is very famous having called at almost every pier/ harbour in the UK and her addition to the game would no doubt boost the sales of Shipsim in the UK. She would be a offer unique challenges to the sim in that being a paddle steamer she has completely different handling abilites from the modern vessels.
Perhaps for passenger ships/ferries such as Waverley a "keep to the timetable" style mission could be developed and included?
There is now a fantastic virtual tour of Waverley online at
http://www.billward.org/pages_wav/waverly.html
Also be sure to look at
http://www.billward.org/pages_ferry/map/map_ferry.html
and
http://www.billward.org/pages_waterbus/index_waterbus.html
and
http://www.billward.org/pages_kenil/start_kenil.html
to see why, Waverley's homeground in Scotland, the Firth of Clyde would be an ideal area to include in shipsim, in a relatively small area there are 11 different ferry routes including passenger & car ferries, waterbuses, a large seacat, a container terminal, a nuclear submarine base, tiny villages, towns, cities, victorian style piers, ferry terminals, fishing ports, drydocks etc