I went to a GW store some odd weeks ago and had a discussion with the guy there about HE core and such. He told me a bunch of ways I could mash kits together to make unique looking HE models. I didn't want to do that, so I asked him how allies work in fantasy(I played 40k for a little while, and knew how it worked in that game). He told me as long as they're from the same faction I.e. order and destruction, it works like 40k. I take a general and two unit types from said book, and whatever else I'd like, but the book specific magic items can't transfer.
Wow, that guy spun you a line there. That may be OK in his store, when he's working there specifically to tell people he's said that, but try that literally anywhere else and you'll have an uproar...
Allies are quite explicitly described in the BRB and at no point does it support what he told you at all. In short you got a GW employee who plays 40k, but not fantasy outside of the bare minimum required for his job, and as such he doesn't know the rules (sadly more common than you'd think). Allied armies are designed primarily to allow 4 player team games, it's assumed you have two separate armies each with their own general, their own units, and therefore, their own core. The rules decide how inspiring presence, psychology, and magic effect allied armies; nothing more.
There are now exceptions to this though. With some books allied troops have been added; namely Tamurkhan, Nagash, and Glottkin. Tamurkhan is the forgeworld book that includes rules for a fragile chaos alliance, as well as rules for including Chaos Dwarfs in standard Warriors Of Chaos. Nagash has rules for including Vampire Counts in Tomb Kings and vice versa, as well as the Lore Of Undeath that allows any army to raise Undead. Glottkin includes rules for a true merging of all the Chaos armies, meaning you can now include Warriors in a Daemons army, Daemons in a Beastmen army etc. All three armies Warriors Of Chaos, Daemons Of Chaos and Beastmen are in effect interchangable (like they used to be way back in 5th/6th Edition). This reaches a zenith when it becomes clear that a Warriors Of Chaos army, specifically with a Warriors Of Chaos general; can legitimately include units from Daemons, Beastmen, Chaos Dwarfs, as well as summon Vampire Counts, and Tomb Kings using Lore Of Undeath, and the various monsters/units from Storm Of Magic without using any "allied army" rules at all... unfortunately the armies of order don't have nearly as much freedom; you're limited to Storm Of Magic and Lore Of Undeath if you can justify it.
If you're playing friendlies you could ask if they'd be willing to play with 'Dogs Of War' from the previous editions as a house rule. This would allow you to take units from an allied army in your army, but they would count as rare units. Again though this isn't officially in the rules. You could have a friendly agreement that you can include say, up to 25% in points from outside armies (which I believe was a rule from way back in 4th edition); but at this point we're effectively suggesting house rules.
I don't mean to be rude, but that GW employee is a damn liar. Clearly he was more focused on selling you mini's than getting the rules right and he outright bullshitted in order to sell you units from different armies you'll never be able to use together outside of his bizarre fraken-games. I'd be shocked if the average fantasy player doesn't get extremely pissed off by that suggestion that GW employee gave you, because frankly it's broken. Trust me, if I only need two units from my main book and they don't even need to be core, you're seeing Chaos Warriors in my Orcs & Goblins army, Dark Elf Darkshards in my Warriors Of Chaos army (core ranged infantry, hell yes). Vampire Counts Cairn Wraiths are going in every army I run, because ethereal is hilarious. I'll be including Sabretusks and Ironblasters in basically every army I run too... Honestly a Warriors Of Chaos army with a few loose Cairn Wraiths, Night Goblin chaff, a bunker of Dreadshards, and Ironblasters and Sabretusks on my flanks woukd be sick... with Hellcannons, Chaos Knights, and Trolls making up my center I could be the most broken miss-match general on the planet. Seriously, that staff member was talking through his arse, he was talking steaming arse ragoo of the highest order.
What I don't like about the SH kit is that its simply outdated, and block looking.
The spearmen look better but still not what I like. I thought of mashing them with the eternal guard kit if I end up using them. Their gilded shields look nice.
The ellyrian reavers are cool looking, but come with a champ which I'd never take, and no muse which I usually do take.
You mentioned the dresses. I think they look good on phoenix guard and swordmaster and all else.
Anyway, if its not acceptable even in friendly games I suppose I'll start looking for some artistic inspiration.
If you're wondering why Id rather not make my own original models, its because it seems like it could easily become a lot of work and I'll end up sinking a lot of money into doing it by buying x amount of kits to mash into let's say spearmen.
It's quite easy to manipulate the system into allowing most things. I have a massive unit of Nurgle Marauders that are actually Bretonnian Men At Arms painted to look extra nurgly... They represents parts of the armies of man that have fallen to the worship of Chaos. One that I really liked was a unit of Skeletons using the character Krell, being used as Warriors Of Chaos. I just gave them Chaos Shields, and painted them "Chaosy", and then field them with the Wailing Banner as their units magic banner and the Crown Of Command on "Krell", after all, "not even death can keep the servants of Chaos from serving the ruinous powers". It makes for a very cool, characterful unit. Before today I've planned a corrupted and mutated Tzeentch army built largely out of Tyranids. Inventive planning can work, you just need to come up with ways to be artistically creative.