You make a very good point, and I guess it's one reason custom translations aren't accepted into the album title field. I personally think the context of 遥かなる時 with 彼方 suggests that 遥かなる時 is the future since going beyond the future, infinity, etc are
common concepts while going beyond the past is not since "beyond"
suggests going in a forward direction and the phrase would be somewhat counter-intuitive (this is translating 彼方 as beyond which also doesn't have to be the case). To illustrate this point, if I say "beyond the past", don't you still think of the future? Fun link:
this Japanese website translates our exact same phrase, 遥かなる時の彼方へ, as "further in the future". There are also multiple results for 遥かなる時 being the future, but of course that doesn't mean that phrase is limited to that translation here.
Regarding the use of 未来 instead, sure, but translations don't always have to literally read what is said. Take for example 獅子の星霊. Go ahead and translate it "the star soul of the lion" if you want, I prefer "Leo" and thankfully
so does VGMdb. If you always try to cram in every word said in a different language from a different culture, you can get some weird and rather stiff translations. Of course, others will say they just could have used 獅子座 or 獅子宮 or レオ if they wanted Leo. I don't so much care to limit myself to saying only exactly what's said if an alternative exists that they could have used instead, translating would be a very rigid process otherwise.
As a sort of reply to your post, your translation isn't exactly my cup of tea since "space" really comes from nowhere. 遥かなる is far away/distant (an adjective, not a noun literally describing actual "distance" so I don't see the reach to it being real "space"), 時 is time, 彼方 is beyond/across. Really no room to interpret "space" popping up in there but I wouldn't be surprised if you could make a case for it
By the way, I love Chrono Trigger, I've played the original and its PlayStation re-release from beginning to end, it's a great game.