Any pantheist Buddhists? I know a lot of the Kyoto school were / have been defined as being as panentheists: but were there any pantheist Buddhists? And, has any comparative religion scholar defined it as pantheism?
Samuel Beal (1825-89), in his translation of the Fo-Sho-Hing-Tsan-King (A Life of Buddha), has defined the Vaipulya stage of Northern Buddhism as a pure form of Pantheism:

Northern Buddhism, again, may be divided into two, if not three, distinct periods of development, or epochs. 
...
Thirdly, the 'indefinitely expanded' form, known as Vaipulya, which is founded on the idea of a universal nature, to which all living things belong, and which, by recovering itself in each case, secures for the subject complete restoration to the one nature from which all living things have wandered. This is evidently a form of pure Pantheism, and denotes the period when the distinctive belief of Buddhism merged into later Brahmanism, if indeed it did not originate it.
Source: The Fo-Sho-Hing-Tsan-King (A Life of Buddha)

The following Sutras are commonly defined as Vaipalya Sutras:

The nine Dharma Paryaya texts are otherwise named vaipulya sūtra, because vaipulya literary means 'extensive'. Nine Dharma Paryāyas are generally enumerated as follows:
Aṣṭasāhasrikā-prajñāpāramitā-sūtra 
Saddharma-puṇdarīka-sūtra
Lalitavistara-sūtra
Laṇkāvatāra-sūtra / Saddharma-Laṇkāvatāra-sūtra
Suvarṇa-prabhāsa-sūtra
Kāraṇḍyavyūha-sūtra / Gaṇḍavyūha-sūtra
Tathāgataguhyka-sūtra / Tathāgataguṇa-jñāna-sūtra
Samādhirāja-sūtra
Daśabhūmīśvara-sūtra.
Source

According to the Dictionary Of Chinese Buddhist Terms:

Vaipulya is extension, spaciousness, widespread, and this is the idea expressed both in 廣 broad, widespread, as opposed to narrow, restricted, and in 等 levelled up, equal everywhere, universal. These terms suggest the broadening of the basis of Buddhism, as is found in Mahāyāna. The Vaipulya works are styled sutras, for the broad doctrine of universalism, very different from the traditional account of his discourses, is put into the mouth of the Buddha in wider, or universal aspect.