[otrs] Transition between two firewalls - parallel setup?

Hi, During my Checkpoint to pfSense transition, I'll have, during a few days, two ISP active at the same time at the office. The firewall is the only router of the organisation, but has several networks attached to it. Would it be possible to have the two firewalls active at the same time and migrate my services one by one? It doesn't matter if I can't migrate all of my services without interruptions, but if I could test a few things on the new setup before the cutover, it would be nice. Thanks, Ugo