it would look a bit odd as independant characters in terminator armour may not lead or be attached to a command squad, they may join it during the course of play however, but unless theres a rule in the main rule book (i havent got it to hand at the mo) then technically i suppose theres nothing to stop you, however, if you were to go down that route (i assume you would give term armour to the champion, apothecary and sergeant aswel) there would be at least one marine still in power armour as the min squad size is 5 and only four marines in the command squad has access to the armoury
ref giving a term a standard, there's no mention that you can make a term in the command squad the standard, HOWEVER, has any one noticed that banners standards etc in the armoury has a little 't' next to the entry? indicating that these things may be taken by marines in terminator armour....
.....just a thought. :wink: