Interesting Ideas I would Love. Please add to this.

[Enkidoh]

Race Options / Clans:
Ishgardian

Ishgardian elezen are literally just wildwood elezen with

traces of Ratattoskr's draconic aether in their souls

, so there physically is no difference to the 'regular' elezen clans the player has access to. For that matter, Ishgardian hyur are exactly the same, they too

share the draconic taint within their aether

so apart from that aspect there is nothing setting them apart as different to the player accessable clans. Also it would kind of derail the whole reason the player is able to be DRG and resist Nidhogg's will during the game's story, unlike Estinien, who is a pureblood Ishgardian. So that pretty much says a big "no" to that ever happening.

Garlean

Again, like the Ishgardian example above, the lore makes it very clear pureblood Garleans cannot use magic (well, in some extremely rare instances they can, but to allow a player character to do that would be stretching credibility too far). And really, how different are they from Highlander hyur other than that silly third eye? (which you can somewhat replicate during character creation anyway with facial adornments). This won't happen either sadly.

Dwarves
Hume
Ronso
Mystel

These are literally just what the Source races are called on the First, and as you can't start the game on the First, this makes zero sense (the player's ability to travel across dimensions was an exception that has now been disabled permenantly). If you want to roleplay as one, change your character's name to a First-centric name and say you're that race from the First. SE will never implement this I'm sorry to say.

Gear Ideas:
Dragoon spear that's smaller/ FFXI design

Smaller? I remember FFXI spears were rather huge and ostentatious, but more glamour is always good!

Cid Dark Knight armor to match helm

I.. take it you mean FFIV's Cecil DRK armour to match the Baron Helm. Which I agree with, but, you can sort of get the same effect with Odin's armour, although that prevents the use of handwear.

A F/C banner that's usable. Hold / carry

Now this I agree with! I'd love a customizable banner as a housing furnishing that could display your FC crest on it (there is already the sign above the entrance outside, but I'm talking about an indoor furnishing). The FC chest already displays the crest anyway so it is capable of being displayed indoors. An accessory to hold that displays the crest would be nice to have too.

Cross over Ideas:
.Hack - Net Slum Dungeon / Raid
White Knight Chronicles/ Sun King Fight (Trial)
Log Horizon Akiba Raid (Abyssal Shaft)

SE seem to be very selective with their crossover events - specifically they seem to pick licences that SE have proffesional connections with, or Yoshi himself has personal connections (such as the FFXIII event being a 'returning the favour' to Motomu Toriyama featuring Lightning gaining miqo'te starting armour and Grand Company swords in Lightning Returns). I'm not sure what sort of legal wrangling between the men and women with briefcases in boardrooms goes on behind the scenes to allow such crossovers in FFXIV with intellectual properties not SE's own, but I presume it's very complex.

FFXI Tavnazia battle a raid or dungeon

We have already had two special FFXI crossover events over the years, and none were dungeons or raids - they were FATES instead (the first featured a giant Shantotto, the second event was meant to emulate various battles in FFXI, such as 'dooms parties' against Robber Crabs, hunting Serkhet in Altepa Desert, hunting Kindred in Castle Zvahl and Xarcabard, and finally emulating the city mission rank 1.3 battle against Spotter and Dark Dragon). These haven't run for quite a while but it's possible SE may bring them back eventually, like they've done with the FFXV event that is currently running.

Abyssal Shaft could also be a deep dungeon

I... have no idea what this is I'm sorry.

Open World Changes:
Open World dungeons

Yoshi already dismissed this back during the Beta test as he wants dungeons to be instanced content (he gave his reasons for at the time, but I cannot remember them I'm afraid, I just remember he was quite firm on open dungeons not coming back). Considering FFXIV 1.0's public dungeons were generally just big underground expanses of nothing, save for an occassional NM, we're not missing much.

Secret monster lairs

We have this already, it's called Treasure Maps and the Aquopolis.

Hidden quests

Again we somewhat have this, there was that quest in Thanalan near Vesper Bay that gave you no assistance on how to complete it, and the ways to do it are completely random, so even online guides are no help. It's clear this was an experiment which SE considered a failure though (as you only got a tiny bit of gil as a reward, although there is an achievement it grants too), so I do not see doing this again.

Lore scattered through areas

There is lore like this, but it's very obscure, and hidden in places you wouldn't expect. Also it's sort of hidden in the sidequests in each area, but again you have to join the dots with a lot of things.

Hidden mini Bosses

We already have this. It is called The Hunt (specifically, rank A and S/SS Hunts).

Player VS Player
Arena in Ul'dah usable

This won't happen. SE doesn't want players idling around the GLA's Guild and adding to Ul'dah's already notorious lag, hence PvP is in the Wolves' Den, it's an entirelly seperate zone. Also the Colleseum is technically reserved for GLA/PLD's only lore wise, so yeah, if you're another class you're out of luck I'm afraid (the PLD Job quests have you fighting there so it's not entirelly wasted).

Team tournaments 2v2 3v3 8v8 with standings

I don't really do PvP but from what I remember the original Wolves' Den tournament was like this. Players hated it and so SE removed it. So I don't see this returning.

Classes:
Blue Mage changed from limited to full class

I'm pretty sure SE do have this as an ultimate goal in the future, but at the moment it's an experiment they're tinkering with so it's best to have patience.

Puppet master or beast master for pet class

Yoshi hates pet classes, as they're notoriously difficult to balance, which explains why the upcoming Reaper class's vaunted voidsent familar apparently is not actually a pet at all but merely a form of weapon/attack they use. And given the ongoing issues ACN/SMN/SCH have with their pets, and the degradation of MCH's turrets, it's clear SE simply are not interested in new pet Jobs being added I'm sorry to say.