Random,
Derishat Zion was the “admissibility of the observance of sacrifices in Jerusalem at the present day.”
“Gaon, can you inform us as to whether that was a discussion of the issue or a presentation of the idea that it was indeed permissible?”
Rav Zvi hirsh Kalisher seriously believed that Public Sacrifices (i.e. Karbon Tzibur) are permissible nowadays. There were some that agreed with him, but most disagreed with him. Some in theory, and some for technical reasons only, and some for both:
See the link below the reason of the Yeshuos Malko of the Gaon of Kutno, which was more of a technical issue (Note, the reason given might be possible nowadays) :
http://hebrewbooks.org/pdfpager.aspx?req=38529&st=&pgnum=5
See the below link – the responsum of the ‘Aruch Laner’ wherein he corresponded with Rav Kalisher in the very first couple of chapters of his responsa Binyon Zion.
http://hebrewbooks.org/pdfpager.aspx?req=591&st=&pgnum=4
Also see the write up from Rav Dovid Friedman of Karlin in the following link: