Hallo Paul,

if effective board area does not become too big and if you take care about ESD, then, why not? If you use 74HCMOS chips, copper traces should not be longer than about 20cm, otherwise transmission line effects will occure (you know, that stuff with reflections etc.). Try to extend concept of solid groundplane over area of slots. So, one side of your slot pins should transport ground.
Keep in mind, that inserting of too many bus drivers can erode bus timing, especially if you run mcu with very high frequency. So, use of rather low clock frequency in combination with small board area concept, which results in short signal traces, would be recomended.

Good luck,
Kai