A big belly able to launch / drop all kinds of stuff (e.g SAR, UAV).
A big radar able to map / monitor large areas.
Moderate stealth (you can't see it from 200nm's)
1. How do you intend to load 'all kinds of stuff' into the 'big belly'? There appears to be no provision for any weapon bay doors - the same probelm as A400M would have faced when it was proposed as the 'FLA', to include Nimrod replacement.
2. Anything with a 'big radar' is unlikely to have 'moderate stealth'! Neither are contrarotating 8-blade scimitar propellers going to give you any stealth.
3. What significant advantage do you see in a high-wing configuration? An overly robust structure implies a poor fuel fraction, something of a disadvantage in any AAR aircraft. As would have been the case with A400M/FLA as a tanker.
4. A single centreline hose would give you a single point of failure risk - not much help if you're considering long-range SAR. Dual Mk-80x Cobham units would be plausible.
5. Upon what is your '18 hours airtime' predicated?
6. Have you done any weight or performance estimations?