The marriage never took place because Alys was keep in custody by Henry II and was rumored to being his mistress and so after his father's death Richard decided he will never marry her. If Henry had married her to Richard when they had the right age that match would have likely great consequences:
1) it will reinforced the alliance between Richard and Philip August (who were often allies against Henry when he was alive)
2) will remove the cause of the antagonism between Richard and Philip during the third Crusade (who was caused exactly by the broken engagement and Richard subsequent marriage)
so the consequences of a such wedding are important also in a like OTL situation.
Professor you had make a little confusion here: Adele of Champagne was Louis VII's third wife (and the mother of his OTL heir Philip August and Agnes) while Alys and her older sister Marguerite (also daughter-in-law of Henry II as wife of Henry, the Young King) were daughters of the second wife Constance of Castile
Okay interesting, so let's say the children of Richard and Alys are:
Richard b 1174
Eleanor b 1176
Henry b 1178
Beregaria b 1180
What consequences and fun stuff does this now bring?