I have read the suggested comparatives with interest. Very few have mentioned the most obvious and substantive comparative which is Hull City. Plymouth is often described as a 'northern city on the south coast'. Some of the parallels between Hull and Plymouth are most interesting apart from the obvious of them both sharing a waterside and dockland setting.
Hull's population is just under 250,000. Plymouth is just over. Both cities are the main regional centre in their respective counties of West Riding and Devon. Both have unitary responsibility separate from the county they are within.
The nearest Football League teams in Yorkshire to Hull are Doncaster and York, both around 45 miles from Hull - about the same distance Plymouth is from Exeter. (Scunthorpe is nearer to Hull but across the Humber and geographically very separate). The combined catchment of the East and West Riding of Yorkshire is around 2.2m. Devon, Cornwall and Plymouth is just less than 2m. Both cities have indoor arenas that can accommodate around 4,000 people but the Hull Arena has a full size ice rink and ice hockey team.
The KC Stadium was built with public money, by the Council, at the same time (approximately) as Phase 1 was complete in 2002. Both Councils own their respective stadiums. The KC also has a major sport and recreation centre alongside it and is set in a parkland setting very much like Home Park. The capacity of the KC is just over 25,000 with two tiers on three sides and a third tier on the West Stand. The stadium is of course shared with rugby.
During the two years in the Championship prior to their promotion into the Premiership their attendances were averaging 18,000. In their first year in the Premiership they were 24,000 although they have slipped a little this season.
For discussion purposes it would appear that by using the strikingly similar parallel of Hull City, the needs of Argyle could be met with a sub 20,000 capacity stadium but a sustained stay in the Premiership would demand an additional capacity of around 5,000. Perhaps this should be borne in mind when the club discuss its grandstand plans with the Council. It would appear imperative that there should be no impediment to the ability to increase the capacity of the stadium by at least 5,000 in the future.