Fir trees, genus Abies are used for bonsai, but not as commonly as spruce, Picea. There are no "big issues" against fir trees. Abies balsamea, the balsam fir, is a cool climate tree, it is only native to the northern tier of states in the USA and most of Canada. It can be tricky getting through very hot summers. But if balsam fir seedlings are native to your local area, then your summers are cool enough. The bark of the trunks tends to remain smooth until the tree has significant age, but otherwise they are fine for bonsai. Give it a go.