The following BIDS Validator issues should be implementable without further changes to the schema:

• TOO_FEW_AUTHORS (length(json.Authors) > 1, select dataset_description.json)
• SLICETIMING_VALUES_GREATOR_THAN_REPETITION_TIME
• EFFECTIVEECHOSPACING_TOO_LARGE
• ECHOTIME1_2_DIFFERENCE_UNREASONABLE (phasediff only; implementing for phase1/phase2 would be a bonus)
• SLICETIMING_ELEMENTS
• REPETITIONTIME_PREPARATION_NOT_CONSISTENT
• VOLUME_TIMING_AND_REPETITION_TIME_MUTUALLY_EXCLUSIVE (needs issue annotation, possibly reimplement in checks)
• NIFTI_DIMENSION
• NIFTI_UNIT
• NIFTI_PIXDIM
• BOLD_NOT_4D
• SFORM_AND_QFORM_IN_IMAGE_HEADER_ARE_ZERO
• NIFTI_PIXDIM4 Implementation detail of old Nifti parser; covered by BOLD_NOT_4D and REPETITION_TIME_MISMATCH
• MAGNITUDE_FILE_WITH_TOO_MANY_DIMENSIONS
• T1W_FILE_WITH_TOO_MANY_DIMENSIONS
• REPETITION_TIME_GREATER_THAN
• ECHO_TIME_GREATER_THAN
• ECHO_TIME_DIFFERENCE_GREATER_THAN
• TOTAL_READOUT_TIME_GREATER_THAN
• REPETITION_TIME_MISMATCH
• EFFECTIVEECHOSPACING_LARGER_THAN_TOTALREADOUTTIME
• POST_LABELING_DELAY_GREATER
• BOLUS_CUT_OFF_DELAY_TIME_GREATER
• LABELING_DURATION_GREATER
• ECHO_TIME_ELEMENTS
• "Participants age 89 or higher" (yes, this really is the code; change it to something consistent)
• MISSING_TSV_COLUMN_IEEG_CHANNELS - Update rules.tabular_data.ieeg.iEEGChannels.initial_columns
• MISSING_TSV_COLUMN_IEEG_ELECTRODES - Update rules.tabular_data.ieeg.iEEGElectroes.initial_columns
• STIMULUS_FILE_MISSING - checks: [exists(columns.stim_file, "stimuli") == length(columns.stim_file)]

The following issues can be implemented at present by using the selector path == '/dataset_description.json' to ensure that they're only run once (a different approach may be justified later):

• SAMPLES_TSV_MISSING
• SUBJECT_FOLDERS
• PARTICIPANT_ID_MISMATCH
• PHENOTYPE_SUBJECTS_MISSING