Coming back from a break and started the process of getting all of my toons to 75 before i focus on a single toon for gearing...though i have my Knight at 274 now. I have gotten my mercBH and about to get my Shadow to 75, but i was left pondering on what to do with all the Ikoath and Gemini gear(s) that have currently in my cargo hold. Is there any reason to keep them if i am getting masterwork gear from FPs as i level up to 75 and, as in the case of my merc, getting a few 270 pieces?

i am a hoarder...i freely admit that...but i would rather save space for items i do want to keep rather than items that just are not worth it; and, to be honest, i wont use most of that gear for appearance.

and i would like to add, barrels should be universal...got a new 258 pistol...was going to change out my 248, but found out that, yes, when it says main hand it means main hand. sigh. thankfully i had some offhand barrels in stock so that i didnt lose out too much.

The set bonuses all moved to the shells, and the old shells are still character-bound, so unless you like the looks of them(1), there's very little point in keeping them once you reach 75, because the old pre-6.0 set bonuses are deactivated on level 75 characters.

(1) If so, keep them so that you can rebuild your Outfit Designer slots if you ever move the character to another server.

Hold onto any shells you may use for outfits, and sell the rest to clear up inventory / cargo space. Their set bonuses are obselete and will not give any effects once a player reaches level 75.

All of the Masterwork equipment (252 and 258 rating equipment) that drops from content between level 70-74 is BoE (Bind on Equip), so you can sell it on the GTN to build up a stock of credits which is a necessity for gearing at level 75. Some of the old equipment (Masterwork, Eternal Commander) have lookalike set bonus armor sets available for purchase at level 75. You may even receive some of these pieces from the gear boxes that drop from completing PvE or PvP content (whichever is your preference).

If you like the appearance of the GEMINI / Iokath armor sets, hold onto those. Sell them to a vendor if not, and do the same with the Eternal Commander armor sets. Sell any Masterwork pieces you obtain when leveling alts from level 70-74 on the GTN if you don't plan on using it for outfit designer. I have found that Masterwork pieces can generate up to a few million credits each (On Star Forge; I am unaware of their going rates on the other servers). These credits will help out a lot at level 75 since all pieces of gear, regardless of purchasing from Kai Zyyken or the class vendors will cost you upwards of a million credits per piece.

..and i would like to add, barrels should be universal...got a new 258 pistol...was going to change out my 248, but found out that, yes, when it says main hand it means main hand.

The good news is that the new barrels from 6.0 are universal. Also, the armorings are no longer slot-locked.

They really need to add some kind of stored/unlocked wardrobe feature like WoW, GW2, etc, where every gear piece you've acquired goes into a virtual inventory that can be used to stamp over whatever you're currently wearing without having to keep the armor pieces in your inventory.

Wildstar probably had the best version of this system as it had the unlocked gear pieces wardrobe like WoW along with the multiple outfits slots like SWTOR.

[...]what to do with all the Ikoath and Gemini gear(s) that have currently in my cargo hold. Is there any reason to keep them [...]?

nope... deconstruct or vendor

and i would like to add, barrels should be universal....

thankfully, at 268+ they are