That should be possible. But it should be much easier and faster to increase the amount of demons that spawn per pentagram. Would increasing the amount of demons spawned work for you hack n' slashing guys (since it would be considerably faster/easier)?
Note that I was planning on updating pents eventually with some strong groups of demons with special abilities in certain areas.
Yes, i think there are some pent zones that could use a few additional pentagrams, but maybe if you just lowered the number of pents required to solve and increased the number of demons spawned per pent, it would be fine. Having to hit 25 pents to solve when penting alone is a little much. Reduce the solve requirement and boost demons spawned... Win-Win.
I started adding 'named' demon bosses at the end of pents. Currently, I only added one at the end of ice pents. After I'm done tweaking that, I will start workin on fire pents, earth pents, and then hell pents. The bossess will have increased drop rate, and (probably) a one-off class specific reward.