We're starting to get into the sort of advice I charge $$$ for...
You don't need an entity to contract offshore, but if you're doing foreign R&D you're savings generally would be less than you would get back with the R&D credit. If for some reason your savings are greater with fully-offshored R&D, you need to ask yourself serious questions about why it's so much cheaper--including the likelihood that your R&D is being shared with the contractors' other clients if you're using an Indian or Chinese contractor.
You're also going to have IP valuation issues due to those risks, meaning that the IP simply won't be worth much, if anything, to a US or EU buyer, compared to the same IP generated anywhere by a subsidiary.
From a GILTI perspective, your IP is now foreign-generated IP, so you're looking at potentially paying the GILTI tax if you sell resulting products outside of the US.
There are additional legal considerations that apply to outsourced R&D development as well.
I do know that certain countries limit what you can send them as far as $ each month as part of anti-money laundering regulations. And it's a pain.
What other implications are there? Is it because some of the offshoring countries force you to register there to conduct business?
Or is it because they want to create a separate P&L for tax and/or liability purposes? Or to park IP?