Draft changes to BaseModel for multi-fitting #1690

Job	Run time
style	29s
Test examples (ubuntu-latest / Python 3.12)	13m 32s
Test examples (windows-latest / Python 3.12)	14m 13s
Integration tests (ubuntu-latest / Python 3.12)	5m 32s
Coverage tests (macos-14 / Python 3.12)	1m 5s
Test examples (macos-13 / Python 3.12)	17m 2s
Integration tests (windows-latest / Python 3.12)	7m 14s
Unit tests (ubuntu-latest / Python 3.9)	1m 12s
Test examples (macos-14 / Python 3.12)	6m 14s
Integration tests (macos-13 / Python 3.12)	7m 58s
Unit tests (ubuntu-latest / Python 3.10)	1m 3s
Integration tests (macos-14 / Python 3.12)	2m 44s
Unit tests (ubuntu-latest / Python 3.11)	1m 7s
Unit tests (ubuntu-latest / Python 3.12)	1m 3s
Unit tests (windows-latest / Python 3.9)	3m 49s
Unit tests (windows-latest / Python 3.10)	2m 5s
Unit tests (windows-latest / Python 3.11)	3m 5s
Unit tests (windows-latest / Python 3.12)	2m 54s
Unit tests (macos-13 / Python 3.9)	1m 58s
Unit tests (macos-13 / Python 3.10)	1m 36s
Unit tests (macos-13 / Python 3.11)	2m 6s
Unit tests (macos-13 / Python 3.12)	1m 29s
Unit tests (macos-14 / Python 3.9)	1m 9s
Unit tests (macos-14 / Python 3.10)	1m 3s
Unit tests (macos-14 / Python 3.11)	45s
	1h 42m 27s

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