Honestly, I would get my hopes up too much for diorama's (yet). There has been only one set announced so far, it's not that LEGO is launching a whole range with several waves each year (like they do with other IP's, that have a theme with both bigger and smaller sets). They're also keeping it into the Icons theme so far, it's not a separate theme like SW, HP, etc.
A lot will probably hinge on how well this set is going to sell, but to me it looks more like LEGO is going to treat Star Trek like they do IP's such as LOTR or Zelda: one big Icons set a year - perhaps one or two smaller sets to accompany them and if we're lucky a CMF-series.
And if that's the case, it will probably more 'generic' sets (like starships, shuttlecraft, etc.) that appeal to a broader audience than smaller diorama's which will appeal more to Trek fans only (although I'd wager my money on one of the Enterprise bridges).
Not trying to be a party pooper btw, but just being realistic - I really don't think we'll get the same amount of sets that Bluebrixx released.
Barclay has only 5 TNG appearances, unless you count his cameo on First Contact. The majority of his appearances (6) was actually on Voyager.
For me, Ro was a way more prominent character than Barclay (on TNG at least). 6 of her 8 appearances were in season 5 and they were obviously setting her up for more appearances in season 6 and 7 (since a few of her season 5 appearances don't really revolve around her as a character, but she's just treated as a regular member of the bridge crew), but Forbes notoriously didn't want to commit herself to a show fully (hence her character being rewritten into Kira for DS9, and later B'Ellanna Torres for Voyager - for which they tried to get Forbes as well).