Randomness in the spells found is not a bad idea per se, but would create serious balance issues, as sometimes you will get crap, some other times a very good "pick", etc .. In MP it'll be a big problem (heck, I have no Seasonal Spirits summons !!
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That was what happened in MoM with the "random" picks, and it was partly balanced with "sure" picks that you made at start.
However I like the idea of uncertainty : for example research could be somewhat randomized and give 50-150% "return rate" per turn. ie if you put a mage with research 10 at work it'll give 5 to 15 points progress, not always 10.
This would be simple, and the global amount of randomness will cancel to average over a game, but will be a small fun plus when you get - or not- your spells 1 or 2 turns earlier or later
