There are two possibilities
The bodice allows the wearer to cast Enlarge
Unfortunately, you cannot combine the effects.
The effects of different spells add together while the durations of those spells overlap. The effects of the same spell cast multiple times don't combine, however. Instead, the most potent effect--such as the highest bonus--from those castings applies while their durations overlap, or the most recent effect applies if the castings are equally potent and their durations overlap.
So if the bodice is just casting the spell, it won't work. Now, it's entirely possible that as a DM you can rule that since it's not quite the same spell, enlarge vs enlarge/reduce, that the effect can combine, in which case you're into homebrew territory. But you'll more then likely want to look at the other possibility.
The bodice has a feature (not spell) to make the wearer larger
This is not unheard of. As mentioned in the comments, the Rune Knight has Giant't Might to make themselves Large. Since this is not a spell, the two can overlap.
In this case, you can review other similar questions:
However, none of which seem to have an answer as far how to play the creature; in other words, what play effects change when you upscale a Medium creature to Huge. And probably for good reason.
If it's just for looks and not abilities, I don't see much trouble.
If it makes a difference to strength, height, weight, weapon damage, radius, attack of opportunity, and other mechanics, you are going to have problems. And a lot of opinions.
Look at how to compute damage:
- Going from Medium to Large via Enlarge you add 1d4 to damage.
- Going from Medium to Large via Giant's Might you add 1d6 to damage (and only once on each of the fighter's turns).
Which means the rules aren't even consistent about increasing one size scale. You're trying to change two size scales (going from Medium to Large to Huge). So do you add 1d4 + 1d6, 2d4, 2d6, 1d8, or some other dice formula?
Now consider that everything you wear will also increase in size. So that two-foot radius shield is now closer to eight-foot (2 * 2 * 2), but still only weighs 6 pounds? That shield is now a sail meaning you could be blown over with a light breeze. You're 15-20 feet tall, but only 200 pounds. Picture a tree with no roots.
I'm not saying don't allow these things to interact (as there are combinations that can work), but and someone asked, Would it be balanced to allow Enlarge/Reduce to double its effect when upcast?, and the answers have a number of different opinions. So if you can avoid including any mechanical changes, merely cosmetic.
One more thing to consider... movement
One of the things I thought about was tanking. At 15x15, they could block most doors, passages, corridors, etc. Then all they need to do is Dodge every round and none shall pass. And per the rule of movement in combat:
You can move through a nonhostile creature's space... Whether a creature is a friend or an enemy, you can't willingly end your move in its space.
So the rest of the party could be on the far side of the tank, walk 10', do a ranged attack, then walk back 10' and be behind cover. No Attack of Opportunity. Complete cheese. But then I read the full entry...
Remember that another creature's space is difficult terrain for you.
So if an ally walked 10' through the tank's space, that's actually 20' of movement. Most creatures wouldn't be able to walk out.
Whether a creature is a friend or an enemy, you can't willingly end your move in its space.
So you're ally would end up in the same space causing issues (DM fiat on how that works).
In contrast, you can move through a hostile creature's space only if the creature is at least two sizes larger or smaller than you.
By becoming Huge, you are no longer a road block. Medium sized enemies and smaller can pass through just as easily as allies. Spend 30' of movement to go under your 15 sq ft cube and it's like you didn't exist.
So since the bad cancels out the good, I don't think it's unfair, but it may make the wearer think twice about growing twice.