I agree - you can probably mitigate #2 with options for the pricing. Perhaps the first option is just the license and customer installs, second is license and you install but they manage any support through Sage and third is a higher level of support.
On random web inquiries like this it's usually all about the discount. They have a quote either with or without a discount and they'd like you to be their (free) third bid to keep the preferred provider honest.
And I'd probably add a number five - Wait time. Every time I've gone to do a remote install for a customer who I don't already have a working relationship with there seem to be a lot of back and forth in order to get me proper remote access, proper login account.
Lastly Sage's partner agreement at times seems to specifically prohibit these types of transactions though it's not well enforced unless a partner makes a beef about your quote.