Since you're asking, here are my oppinions:

- It's a petty that you won't include the dynamic campaign in the inicial release. I disagree with Ripcord when he says that "dynamic campaigns are not that important" (not his exact words but that's what he meant - at least that's what I understood) since nowadays every modern combat flight sim only have static campaigns and that's IMO it's a bit frustrating - I miss the dynamic campaigns of "old-day" sims such as Falcon 4, EECH or Longbow 2. I would prefer much more that you delayed the release date of this first release in order to include the dynamic campaign (similary to what Ubisoft did with Silent Hunter 3 few years ago - a move that worked extremelly well, BTW).

- When you announced this Harrier Gr3 inicial release, I had the similar though as you - this would be a much more limited choise since the Harrier Gr3 ended up doing Air-to-Ground missions exclusively (and not Air-to-Air ones) and the Sea Harrier would be a much better choise BUT then I remebered all the A-10 similations that came up in the past and will come up in the future (DCS A-10) - These sims modeling the A-10 were as expected very limited in Air-to-Air combat content but nevertheless were between the most loved modern combat aircraft sims and aircraft modeled and this was IMO partly or even mainly done with the introduction of interesting Air-to-Ground missions (which often involved close air support of friendly troops).
Anyway, I always thought that the Harrier Gr3 back in the 80's was the RAF counterpart to the USAF A-10, even if the Harrier is lighter, less resistant, faster and somehow more agile and STOVL capable when compared to the A-10 even because the mission of both the A-10 and Harrier Gr3 centered around Close Air Support. So this means that a good idea is to look at missions of previous A-10 simulations (such as A-10 tank killer, A-10 Cuba, etc...) for inspiration.

- Regarding a possible dedicated Air-to-Air role/missions for the Harrier Gr3 in Jet Thunder, my oppinion is:
Avoid it! Well I guess there could ocasionally be one or two (top) Air-to-Air missions during the campaign but except for this you should avoid the Air-to-Air missions and the A-10 simulations prove that these type of missions aren't really that needed for a great combat flight sim. Anyway I know that there is always the need for the "rush of Air-to-Air combats" in any combat flight sim so IMO what should be done in Jet Thunder in order to satisfy this "appetite" is using a similar "formula" used in the A-10 sims which basically is - TARGETS OF OPPORTUNITY - In the case of Jet Thunder this could be done by introducing flights of argentinian aircraft such as Pucaras, or helicopters (Pumas, Hueys, Chinooks, Agusta A-109, etc...) or even faster fighter-type aircraft such as the A-4 nearby the player's mission objective areas (and some of this aircraft could be tasked to attack friendly ground/naval units) thus giving the player the decision wether or not to try to engage and kill some of those enemy aircraft as targets of opportunity (and thus saving some friendly ground/naval units in the "end of the day").