@pyreegueAlthough I don't own any payware airports for MSFS yet (bugs like the 285°C temp bug or disappearing RWY and TWY lights when arriving at night make it absolutely unflyable atm) I'm always super excited when there's news from you!
I've never bought any UK2000 airports for P3D back then, because there was still a bit of room for improvement imho, so I'm very happy for any UK airport you want to recreate in MSFS and I guess a lot of those who already own a UK2000 airport are willing to upgrade to your version too!
Regarding EGLL Heathrow: I personally prefer two mid size airports in the time you'd need to make one Heathrow addon.
If you need a challenge, go for EGLL, you are among the few devs who can create a very accurate Heathrow version but again: I think your talent is better spent on airports like you've done in the past.
Picking up suggestions from @BAW9DV and @carlosqr:
LKPR Praha, VRMM Male, LHBP Budapest (LH Sim version is quite good, so, not a good choice), LYBE Belgrade, LROP Bucarest and LBSF Sofia would be really nice and I'd buy them right away (if MSFS was finally free of major bugs that make your aircraft stuck in the air like it was jelly).
In addition to those good recommendations, I'd LOVE to have a top notch rendition of EFHK Helsinki and the three baltic capitals EETN Tallin, EVRA Riga, EYVI Vilnius. Heading further south and east: HAAB Addis Ababa, LLBG Tel Aviv, UGTB Tiblisi, UDYZ Yerevan, airports in central asian states (if you really want to go off the beaten track) like Türkmenistan, Uzbekistan or Kirgiztan and finally airports in Iran. Most of those airports are perfectly in range for an A320 or A310-300 from Europe, Dubai, India and China.
Anything you'll touch next will be on my shortlist but the only thing that's a no-go for me: If any given airport has got a RWY shorter than 1800-1900m, 'cause I need some TODA to get from your next airport back to Europe or Dubai within a couple hours without clipping the approach lights on the end of the RWY.
Cheers!