That kingdom actually offers a variety of potential ways of handling copper
(1) trash with loan
(2) trash with steward
(3) use labs/cellar to draw a big hand of copper and trash with a mint, restocking quickly with minted gold
(4) use stables to draw big hands by discarding copper then use a cellar to discard the accumulated victory cards for extra draws
(5) use stables to draw through the deck, use a cellar to discard the copper, then take it all back with a counting house
You could also be clever and play a few of those options together or wait and see which way your draws push your deck. Out of all those options though the loan seems the weakest as you'll eventually be depending upon treasure to buy your cards. Put festivals, say, into the kingdom and you can use the festivals to buy your cards and the loan to trash safely.