Agree with OP, more rank and file troop options would be most welcome. Mindless zombies and canine remains come to mind for Ressers...I dont play other factions (yet) but I see that many suggestions have already been made above. I Ordered a horde of zombies from 'Studio Miniatures' in the UK...they are on the spendy side of things ($50 for 17 zombies on Warstore), but are closer to the size and scale (I think, haven't received them in the mail yet) of Wyrd's line of minis. I went ahead and ordered the 'Hats and Guns of Malifaux' so, with some greenstuff, I can convert some of them to fit the period/aesthetic more. 17 is allot of zombies, and most I'll need on the table at any one time is 8 or 9...the rest I can fold into my Zombicide board game when it comes in the mail in August.
I've also played around with the idea of grabbing one or two rank and file models from other factions and "zombifying" them, but this is lower priority for me, I need to paint models I have first!