*snip of a long post about a Grey Wizardly EIC*
This is very clever and thought-out. That said, I remembered an old Boney post about a similar subject and dug it up:
'Information gets passed up the chain so that the EIC can better make business decisions for the profit of everyone involved' is fine with everyone and normal not just for the EIC but for most trading companies. Major Shareholder Dame Weber, hero of the Sieges of the Drakenhofs, can deepen that existing culture without anyone finding it at all unusual. She's an expert at gathering and profiting off information, and the EIC's profits are her profits. Other Grey Wizards won't have her reputation or the presumption of profit motives to protect them, and Grey Journeymen don't have enough experience to take it as given that they'd be able to operate quietly.
If other Grey Wizards are known to become involved, it will be assumed that it's because the EIC is becoming part of the Empire's information-gathering apparatus. And there's nobody in trade who's so without sin that they'd feel fully comfortable doing business with the EIC under those circumstances, even if those sins are entirely limited to being flexible with their tax-paying obligations. This is a time period where the back-and-forth of corporate taxation wasn't done with lobbyists and accountants, it was done by ensuring a safe distance between excisemen and taxable goods by a wide range of methods, some of which might, in a certain light, be considered 'bribery' or 'smuggling'.
Now, the advantage of a known personal connection with Eike is that she can trade off of her connections with both Mathilde and Wilhelmina for plausible deniability, even if she is a known Grey Wizard. But we should
expect that the more closely the EIC is obviously tied to Imperial governmental institutions, the more people will proceed under the assumption "this is an intel-gathering op" and be leery about doing business.
...that said, a world in which the EIC transitions from being a merchant cartel to being the Empire's UPS/FedEx isn't a bad one and is a totally reasonable way it could evolve in the future under hypothetical-Grey-Eike's majority shareholding. Merchants might not be comfortable doing
business deals with a Grey Wizard's known business (Regimand might have a network of owned taverns, but he doesn't own them
openly), but using a Grey Wizard's business strictly for handling overland and riverine shipping? That might get more traction, and it would still give plenty of opportunities to have eyes and ears everywhere.