Connecting vases is the easy part as long as is done fast, or the cut piece is covered and protected from became too dry and develop longitudinal cracks. Just sinking it in running, good quality, freshwater would help for weeks probably. Maybe even months.

First, all leaves and some branches must be removed to avoid fast dehydration. Both surfaces have to be polished to 1) assure a good contact (the chainsaw removes a few centimeter ring of the wood, so you can just put it in place and wait) and 2) achieve perfectly 180 degrees flat surfaces so all the forces are applied vertically and the trunk remains in the same place instead to slip to the right for example.

Then you need to (pressure?) wash the surface to remove any debris and unclog the vases.

next step would be to put both trunks in the exact position with a crane (should be easy part. The trunk section is not a regular circle). The idea would be trying to connect most possible vases at least in a side even if you don't achieve a 100% contact and the other side must end very displaced. As long as you can somehow assure that the weight has accurate support, this is all.

Survival is not guaranteed. no government has been done this before, but any politician succeeding on this would send a strong message, and probably became very popular overnight. Just trying would improve their image.