Did the Romans have parade armour?

[Urselius]

The usage of other times and cultures is relevant because people are people, and they tend to behave in similar ways.

Can you back this up? Anthropology would rather teach that this is not necessarily the case, for a variety of reasons, thus a "Historical Comparison" is a rather difficult and much debated historiographic method. Or what exactly do you mean by "similar", which is, of course, quite a relative term.

Read:

R. Bendix, Herrschaft und Industriearbeit, Untersuchungen über Liberalismus und Autokratie in der Geschichte der Industrialisierung, Frankfurt a. M. 1960.
M. Bloch, Pour une histoire comparée des sociétés européennes (1928), in: Marc Bloch, Mélanges historiques, Bd. 12, ed. by Charles-Edmond Perrin, Paris 1963, p. 16-40.
H.-G.Haupt, J. Kocka (eds.), Geschichte und Vergleich. Ansätze und Ergebnisse international vergleichender Geschichtsschreibung, Frankfurt 1996.
M. Herren, M. Rüesch, C. Sibille, Transcultural History. Theories, Methods, Sources, Heidelberg/Berlin 2011.
B. Moore, Social Origins of Dictatorship and Democracy: Lord and Peasant in the Making of the Modern World, Boston 1966.
C. Tilly, Big Structures, Large Processes, Huge Comparisons, New York 1984.
S. Rokkan, Vergleichende Sozialwissenschaft: Die Entwicklung der inter-kulturellen, inter-gesellschaftlichen und inter-nationalen Forschung, Frankfurt a. M./Berlin/Wien 1972.
P. Flora, E. Fix (Ed.), Stein Rokkan. Staat, Nation und Demokratie in Europa. Die Theorie Stein Rokkans aus seinen gesammelten Werken, Frankfurt a. M. 2000.

I can read French and to a limited degree Anglo-Saxon, but not German.

I think that it is widely understood that human beings are subject to universal motivations, and that, as a single species, basic behaviour patterns are also universal. I cannot imagine that this view is either novel or controversial. See for instance Darwin's Descent of Man.

Take a 'for instance' - apotropaic symbols. We have the 'lucky rabbit's foot' , St. Christopher medals etc. other modern cultures have similar devices, Sri Lanka has rings incorporating elephant bristles, China has elaborate knots in silk cord. The Romans used phallus symbols and 'mano-fica' hands to avert the evil eye or bad luck. Interestingly, they also used goat's penis shaped amulets which have survived to today - they are described as "cornucopia" but they are really pointed goat penises. Universal feelings of threat from 'fate', evil wishes from others, or the workings of chance produce universal responses in apotropaic symbols.

Looking at martial societies, is there evidence of the production of "military" equipment unsuited to practical use in battle?: Rennaisance Europe - yes parade armour, Napoleonic Europe - yes impractical full dress items of dress and officers gorget plates, Sumer - yes a gold helmet (obviously impractical), First Dynasty Egypt - yes stone mace heads far too large to be wielded, Celtic Europe - yes, Battersea shield, the flapping bird helmet from Romania etc. etc.