The Basilisk Centauri took somewhere around a year to complete the design of, as rapid advances in Jaeger tech were being produced every time they thought they had finished improving the design. Byron himself, with the aid of AI, had a huge influence towards it.
The Jaeger had a huge emphasis on the Juggernaut style: capable of taking almost any kind of punishment while dealing twice as much in return. It may be fast, but that is not what it relies on in a fight.
Parts of the Jaeger came from factories around the world; nuclear cores from America, gravitational stabilisers from Australia (designed in New Zealand, mass-produced in Australia), etc. It's final birthplace was the Blue Reef Shatterdome in Fiji.
Byron "Volt-Head" Kraus is the solo pilot of this massive Jaeger. The solo piloting is made possible only through Byron's AI, an electrical implant in his head.
Right at the start of World War Three, Byron offered to let Veronica Martinez and Clarisse Linn pilot it with him - in the last fight he'd been taken out early by an EMP. If there were three Drifters, the dangers of the Basilisk getting taken out would be lessened.