As Kat already explained, the 1.000 soul limit has technical reasons. Its goal is to keep the savegame at a healthy size. Back then when we had no limit at all, we found out the maximum savegame file size the hard way, resulting into permanent crashes. So as much as I understand the interest in an increased limit for patrons, I'd personally suggest to not add such a perk. It would reduce server performance for everyone. Eventually it would not be noticable if only one tribe uses it, but there are plenty of patrons. Just my two cents though from someone who implemented the soul limit back then.
I heard ThumperMan007 is an expert when it comes to soul limits.