Know this post is a little old now but thought I'd post my experience for future board surfers.
Tried the Baileys imitation and the Sambuca imitation.
Baileys one was interesting, instructions said to add cream then the alcohol base. Since my wife is lacto-intolerant this is the one I was looking forward to trying. We added soya cream and the base and made a milk-free variety. It was.... ok. For sure not Baileys but in a hot chocolate it tastes just fine
Sambuca imitation tasted way too aniseed-ey. If anything I'd put less of a bottle in next time or just smash some aniseed up and steep it in a muslin bag.
As far as flavoring goes for alcohol base I've been using the soda stream concentrates, cordial (tescos finest is 2 bottles for £2.50 atm) or just steeping fruit and adding a bit of food coloring.