Taking the OP's suggestion, and changing the iLvl numbers of the gear to i380, and the weapons to i385 upon obtaining it, with a quest item from v10s to upgrade it to i395. Here's how I'd see the points that you bring up:
- Suzaku and 4.5 Primal are useless outside mount farming
The 'base' relic would be at the same iLvl as the Suzaku weapon. The relic would still be better, due to the extra materia slots, but the Suzaku weapon would be a faster less-grindy option. Alternatively, go back to primals dropping accessories, possibly with a rare chance of a weapon (turning glamour into part of the incentive to farm for the weapons).
- Crafted gear markets crash obscenely fast
With relic gear at i380, it would be the same as the Crafted gear, and would boil down to stat combinations, and overmelding vs. 5 guaranteed melds. They could even raise the relic gear to i385 or 390 with the odd-numbered patch, if they decide to augment the crafted gear again (i380>i390, similar to the i350>i360 thing in 4.3).
Crafted weapons sorta get the short end of the stick here.
All in all, it'd come down to "Get gear upgrades now" vs. "Get gear upgrades after a grind", with Alphascale normal being sort of a middle ground.
- Alphascape Normal is obsolete
Both of these would depend on how much of a grind it'd be to get the relic gear/weapon. People who want a less grindy way of gearing would have this as an option, along with the crystalloid from v12.
- Tome weapons are more or less useless
In this scenario, the tomestone weapon would still be 5 iLvls higher than the relic, although its strength should be relatively the same (due to the extra materia slots). Players who grind out the relic fast enough, will be able to obtain a weapon slightly better than the tomestone weapon, before other players get their Scaevan Esters from v11s.
- 24 man gear serves no purpose as a "catch up" drop
Considering what their stance on the "greed-only" thing was, with how they saw 24-man gear to be "catch up" gear for alt jobs, I don't think this would be affected all that much with an increase in relic iLvl
Even then, if they decide to go with raising the relic gear to i385/i390 in the odd-numbered patch, it'd still only be slightly stronger than the 24-man gear.
The relic being a huge grind doesn't necessarily have to be a bad thing, if it's a grind that actually feels rewarding once the player has finished it. This is why it's important to keep it closer to the raid weapon iLvl, and add it earlier. A big reason why I never went from the Pagos weapon was because of when they added it. I just knew that by the time I had obtained it, I'd only be able to enjoy it for maybe a week or two before being able to just grab a higher iLvl crafted or primal weapon.
Raid weapons requiring skill and relic weapons only requiring a pulse has been a thing since post-Titan relic progression, which also isn't a bad thing. It gives players who are unable to raid the ability to work on progressing their character in a meaningful way. Heck, having a quest item drop in v10s to increase the relic to i395 might even be enough incentive to dip their toes into the more midcore part of savage raiding. i395 would still be 10 iLvls below the raid weapon (or closer to 5 when taking the extra 3 relic melds into account).
Because progressing your character is fun.