I'd agree about not restricting yourself for the future, the straw bales could be a good idea but you could just see those distributed in and out of the arc within a day ha ha
Pigs are pretty good at going outside for the loo, i had one last month that wasn't too well, he's in a 8x12' arc with 7 others but as soon as he was up and about he left the arc to do his business.