Let's see...
(warning: not to be taken seriously).
Canon 6D, an entry level camera which will be 3 years old when Pentax will announce their FF. Its MSRP was $2,099.00/£1,799. Pentax would have to launch a "K-x FF" - because the K-S1 is too modern.
Nikon D610, a costly fix for D600's oil spots issue; announced in 2013. Pentax would need a first model with oil spots on the sensor. Perhaps they could collaborate with Nikon on that?
Nikon D750. Hmm... a lucky 3rd try? Can't be done before the oil-spotted "D600" and the expensive fix "D610".
Sony A7 - discounted discontinued discounted discounted model, sold at a discount. Incorporating technologies impossible to replicate by Pentax, e.g. the amazing flexible mount.
Sony A7 II - it's an A7 with a 'II' on its name and an increase in number of metal parts to an amazing two.
Sorry, none of those would work
On a serious note, 2000€ MSRP is entry-level price; and not everyone wants an entry-level cameras and the compromises they bring. $1300 MSRP just won't happen, period (and no, Pentax won't go in a price war with Sony, that would be insane).
Even more, entry level cameras are truly feasible only by heavily reusing already developed components, taken from higher end models; yet this will be the first Pentax FF DSLR.
P.S. I would happily pay only 2000€ or less on an advanced Pentax FF DSLR; however, I don't think such a thing is feasible. I would not want to pay 2000€ or less on a compromised design. No to wobbly mounts, oil spots, APS-C AF put on a FF DSLR, entry level performance and reliability. Since it would be an important sum anyway, I would rather demand
and pay for quality.