title_body: How can I add irregularities to a morphological paradigm? So, I'm trying to make something with a naturalistic feel, even though the current phonetic system distinguishes about 38 phonemes... Let's say I'll tackle this later. 
  I have issues with grammar... I want to use Proto-Kartvelian as a root source but make a language that has Indo-European grammatical structure. So... When I tried making noun declensions I generally end up making something that turns into agglutinitive suffixes... E.g. if we have a masculine noun ending in -o, I simply use consonants after the -o to express cases, then change the -o to -a for plural and repeat. E.g. -o/ -og/ -ot/ -om/ -ol vs -a/ -ag/ -at/ -am/ -al...
   It is too regular. How do I change certain things so that it looks less artificial, but still maintain some logic... I need advice.
upvoted_answer: One possibility: perhaps your "-a- for plural" derives from an ancient word for "many" that was of a different declension, having different endings, so you could posit:
  
  S  -o / -og / -ot / -om / -ol 
  vs
  P  -a / -az / -asis / -amis / -ay
  
  Another possibility: the historical importation of a foreign declension pattern into words of certain classes, which practice later infects native words of other classes either in whole or in part.
  
  Consider the Latin words that have Greek declension and extrapolate from there.
  
  A third possibility: the later "regularisation" of ancient defective words actually introduces an irregularity. For example, your modern word for "mob" might be an ancient plural form of "person", so you could posit:
  
  S -a / -ag / -at / -am / -al
  vs 
  P -a / -az / -asis / -amis / -ay