Seed propagation of rootstocks is generally preferred. The main reason is that seed do not transmit the majority of Citrus diseases, whereas cuttings may have virus or bacterial pathogens. This can then transfer to the scion causing graft take problems or long term problems.
Healthy young plants obtained from approved schemes, may not be a big problem for taking cutting materials, compared to older trees.
Second the roots of cuttings are said to be more fibrous, compared to the tap roots of seedlings.
That could lead to problems anchoring the plant in the soil.
I have found cuttings usually produce a few main roots, so not as big a problem for containers.
Trifoliata is often said to be one of the more difficult Citrus to root as cuttings. Some members here have had success.
Yes there are advantages to working in a greenhouse, both for the worker and the plants.
I would probably bud Citrus at slightly higher temps than those you quote.
Maybe other members could also comment on this one ?