Some considerations for the proclamation of the Word of God:
[61.] In selecting the biblical readings for proclamation in the celebration of Mass, the norms found in the liturgical books are to be followed, [GIRM 356-362] so that indeed “a richer table of the word of God will be prepared for the faithful, and the biblical treasures opened up for them”. [Sacrosanctum Concilium 51]
And this is one of the more successful conciliar reforms.
[62.] It is also illicit to omit or to substitute the prescribed biblical readings on one’s own initiative, and especially “to substitute other, non-biblical texts for the readings and responsorial Psalm, which contain the word of God”. [GIRM 57; Vicesimus quintus annus 13; Dominus Iesus]
Two things here. While there is a tradition within the Liturgy of the Hours to read from the writings of the saints, I don’t see the indulgence for poetry and other texts–Scripture is rich enough. The time for it? In musical texts, perhaps. In the homily. Before and after Mass.
I haven’t seen much in the way of non-Scriptural texts substituted for the psalm. But it would be nice to see that spot opened for canticles from both the Old and New Testament, if we absolutely have to go outside the Psalter.
[63.] “Within the celebration of the Sacred Liturgy, the reading of the Gospel, which is “the high point of the Liturgy of the Word”,[GIRM 60] is reserved by the Church’s tradition to an ordained minister.[Cf. GIRM 59-60] Thus it is not permitted for a layperson, even a religious, to proclaim the Gospel reading in the celebration of Holy Mass, nor in other cases in which the norms do not explicitly permit it. [Cf., e.g., Order of Marriage (1990) 125; Order for Anointing of the Sick and for their Pastoral Care 72.]
One of those cases would be the singing of the Gospel canticle at the Hours. But otherwise, I don’t think a lay person reading the Gospel has been a widespread problem, except perhaps in women’s communities. But that’s an issue other than liturgical, I would say.