not impossible at all
'solid' can mean good, strong, etc... = no problems. (so, not a bad cia)
all cias apart from system and dsiware install to the sd card. there really is no harm in installing a cia when you are not using emunand.
but yes, the cia could be some malicious cia that someone made, it is possible to create one, that ruins homemenu or something etc, so it would effectively brick your 3ds.
if you check out each cia before you install you can be ok. devmenu even tells you if it is a system cia, or a game cia, update cia etc... there really is nothing to worry about.