Do you really need to charge VAT to a business outside Portugal? I thought you can exempt the VAT for foreign business to business transaction. I've actually done that a few times when UK was still in the EU.
What I did to hire workers in Portugal through my UK company was to have them as freelancers. No VAT, and they registered for recibos verdes (=self employed), and pay their own taxes and their own social security (which are high, like in NL).
I talked with an accountant a few weeks ago, and you may have another option:
Set up a Portuguese company, and under the NHR **if** your profession is one of the approved ones, pay only 20% tax on the dividends of that company (no corporation tax for small companies that you own over 75%, which sounds too good to be true, I will ask my accountant again.). Then you could buy a car on the company, and save the VAT and tax on it if it's electric or PHEV.
Or if not under NHR, set up a Dutch company, and have your employer pay the company, and you get paid with dividends in Portugal with 0% Portuguese tax, under NHR again.
You need some serious talks with more than 1 expert accountant.
My accountant which I just started with is All Finance Matters in Tavira. Convenient if you're in the Algarve.