Here is a solution. I think you already solve this problem though.

I guess there's no way to inherit a exists sequence record.

You can write a new sequence.xml below:

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data noupdate="1">

        <record id="seq_new_sale_order" model="ir.sequence">
            <field name="name">Sales Order</field>
            <field name="code">new.sale.order</field>
            <field name="prefix">SO%(y)s</field>
            <field name="padding">5</field>
            <field name="company_id" eval="False"/>
        </record>

    </data>
</openerp>

See this line: <field name="code">new.sale.order</field>

I set field's value to new.sale.order

You should set a name as you want.

And override a create method in sale.order

from openerp import api, models, _

class SaleOrder(models.Model):
    _inherit = 'sale.order'

    @api.model
    def create(self, vals):
        record = super(SaleOrder, self).create(vals)
        record['name'] = self.env['ir.sequence'].next_by_code('kinder.sale.order') or _('New')
        return record

See : record['name'] = self.env['ir.sequence'].next_by_code('kinder.sale.order') or _('New')

You can input sequence new.sale.order by using next_by_code method.

I think there is no way to inherit a sequence xml files.

Instead, you can override a create method.

Have a nice day!