Dear,

Each country offers the possibility to buy a subscription for their charts. Eg: Skyguide for Switzerland, Avioportolano for Italy, DFS for Germany, Rogers for Austria and so on.
Why not to develop an integration with Jeppesen chart? Did you already evaluate this opportunity?
Jeppesen charts (approach, area, etc.) are all the same style and they have essential info specific for VFR flights, and you can find many useful info (PPR? Customs? Etc) in an easy way and in one place (it’s not always easy to find some specific rules for GA flight in Civil Text info for some aerodrome...).

Many thanks for your attention.
Andrea.