In my opinion, posts which assert something can or cannot be done are as credible as 1) their documentation from Church sources, 2) the proper reading of those sources, and 3) the reasons used to develop a position.
Similarly posts which assert that something should or should not be done, even when permitted, are only as persuasive as the reasons. Then they become useful to those who read the threads in the future, and that is an excellent service that posters can offer to others. So I encourage that and add a small contribution now.
Perhaps it would be helpful to consider the documents of the Church in thinking about multiple roles. There are several (in translation) that might be considered. Someone may be aware of other references that should be added that will correct or modify any conclusions that might be drawn from these.
The Constitution on the Sacred Liturgy, n. 28, addresses this. “In liturgical celebrations each person, minister or layman, who has an office to perform, should do (agat) all of, but only, those parts which pertain to his office by the nature of the rite and the principles of liturgy.” “Agat” is the subjunctive which has the force of a mild command, a principle, or a general rule.
MR, General Instruction, 109: “If there are several persons present who are able to exercise the same ministry, nothing forbids their distributing among themselves and performing different parts of the same ministry or duty.”
RS, n. 43 then provides: “It is appropriate (convenit) that a number of persons distribute among themselves and exercise various ministries or different parts of the same ministry.”
So here is the question, is this preceptive law that never admits to exceptions based on need or when suitable reasons appear to the priest in a concrete situation? If so, why? If so, why not?
When we read the context of MR, General Instruction, n. 109 and RS n. 43, we also note that they are addressing certain liturgical roles which have been named in those documents. MR mentions them in nn. 98-107. RS mentions them in nn. 43-47. Bride and groom are not on that list.
How will this fact influence deciding this question of whether it can be done? Of course, whether it should be done if it shifts emphasis from the Eucharist to the Bride and groom is another matter. Who is suited, and permitted in law, to make that judgement whether it will or won’t in a particular case?
See RS 87, of course, regarding first reception of Holy Communion by a priest. There is, of course, a reason for the norm.