What does "autolyco-sentimental" mean?

The quote is not Berlioz but from Wagner’s book-length essay “Oper und Drama” (Opera and Drama). Wagner wrote it in 1851, and it was published the following year in Leipzig.

Your text is just one translation, the one that runs:

Weber wanted a Drama that could pass with all its members, with every scenic nuance, into his noble, soulful Melody: — Meyerbeer, on the contrary, wanted a monstrous piebald, historico-romantic, diabolico-religious, fanatico-libidinous, sacro-frivolous, mysterio-criminal, autolyco-sentimental dramatic hotch-potch, therein to find material for a curious chimeric music, — a want which, owing to the indomitable buckram of his musical temperament, could never be quite suitably supplied.

But here’s another, this time from Edwin Evan’s 1913 translation, where the translator has seized on different wording here:

Weber wanted a libretto of such character as to enable it, at all times and with every scenic shade of colouring, to rise up into his noble soulful melody. Meyerbeer, on the other hand, wanted a huge, parti-coloured, historico-romantic, satanico-pious, dogmatico-lewd, sancto-nonsensical, mystico-daring, sentimentally roguish, stagy conglomeration of all sorts, in order to provide him with the occasion for inventing fearfully curious music which, however, could never prove successful in application, in consequence of the natural thickness of his musical skin.

So this is talking about some “roguish” activity — as Mick notes, alluding to a thieving figure from classical mythology who used tricks to deceive his neighbors.

Seems pretty roguish to me.

Autolyco- From the Greek autolycus, meaning "the wolf itself" (i.e. savage, without sentiment).

Wikipedia: Autolycus

So, autolyco-sentimental is, perhaps, an oxymoron meaning both with and without sentiment.

Also:

Autolycus

Greek mythology

A thief who stole cattle from his neighbour Sisyphus and prevented him from recognizing them by making them invisible

Collins Dictionary