Sorry if this is off-topic but I wasn't sure where to direct the question.

I've just started dabbling in modifying FiM blindbag ponies.  Of course this means I'm slowly amassing a herd of the wee things.  I'm not collecting them for profit or resale - just for the fun of it.  The modding is fun and I hope to eventually recreate some of the background ponies from the show.

What I don't want to do is accidentally mod one that another hard core collector would want, or make a fan have a heart attack because I cut the head off a hard-to-find model so I can add it to my Nerd Herd.

I don't have any plans on using any obvious character pony figures - like Cheese Sandwich, for example.  I've also noticed a few figures are expensive - such as the Zecora from 2013 - and I wouldn't take an exacto knife to anything that (relatively) pricey.  I've found lists of ponies available, but nothing to say if they're a dine a dozen or rarer than hen's teeth.

IS there such a thing as a "rare" or "bait quality/common" blindbag pony, or are they distributed evenly so every one is equally easy/hard to find?  The Main Six seem easy to get ahold of, but are there ones I shouldn't use if I get duplicates?  Is the going rate generally a good indicator of what not to hack into? 

Any info you could give me would be welcomed.