I had frontlines in mind not Blitzkrieg
In HOI4 u also often have static frontlines if the 2 opposing armies are nearly even or the defender has built bunkers and in such situations offensives bring just small just small Land reclamation with high casualties.
And the fastes armies at that time were cavallryunits which could sometimes strike "Blitzlike", regarding the Cavallrybattles between Poland and the Sowjet Union directly after WW1, after which the frontline moved very fast.
And aye, i hate the micromangemengt in vicy 2 after 1970 too-especially when Africa is getting colonized u have to watch such a large territory...most big wars u have to watch at many continents the same time.
That´s why i would prefer a system like in HoI4 in which u can let the AI take over at less important frontlines and u yourself can focus on the main frontlines.
Also, a closed frontline like in WW1 is very very very hard to create in vicy 2-and if u manage it u have to control 15+ armies every day...
In HoI u draw a frontline and the armies take their places themself and close da line.