A fully-loaded scraper is very heavy. Tires generally provide better compaction than tracks.
However, the tires on a loaded scraper are NOT designed for compaction, they are designed to keep the scraper moving in potentially sticky conditions.
Sheepsfoot rollers and vibratory compactors are designed for compaction. They will do a MUCH better job.
Using a liner as insurance is a pretty expensive option. They are not cheap to purchase, and they are a lot of work to install. Also, the design of the pond basin is different when installing a liner.
Personally, I would hire one of the contractors that uses dedicated compaction equipment to build the pond.
