It really comes down to person's individual costume. IMHO, it's like snowtroopers that way - some people look awesome & others not so much. For sure some one will do this and we'll have a different CRL.
As for various armor types, even in a modern military there can be an overlap of equipment that is fielded. Not sure how it is now, but in my era for instance we had just regular BDUs and M16A1s, while the regular army folks had summer weights & M16A2s. My first unit still had jeeps for years before humvees trickled down. It's very conceivable in a huge empire like this that older, functional armor would still be around, especially in the outer rim. Just because new armor gets fielded doesn't mean that everyone has the cash to upgrade immediately.
Heck, look at the USAF - the B2 didn't exactly replace the B52 now, did it? Yup, they are flying airplanes older than 85% of the US population.