Overall, the advantage of true heavy bomber to the Reich would be negligible. There are several reasons for this
- Unescorted bombers tend to suffer crippling losses, especially when most of the mission is over enemy territory. The situation for the Luftwaffe in the East would be pretty much a mirror for the RAF/USAAF effort IOTL, and not the relatively safe quick dashes that marked the Blitz (where the RAF really only had about 100 miles of airspace that they could play defense with).
- Every fighter devoted to bomber escort in the East is one fewer defender in the West. The USAAF used to have roughly one fighter for every three bombers early in the war. Once Doolittle took over, that number went up (although the escort method also changed radically) and hovered at around one escort fighter for every two daylight bombers
- Every heavy bomber means about five fewer fighters available for the Luftwaffe to defend the West. Put another way, every Luftwaffe heavy shot down = an Allied fighter ace.
- The other way the math works is that every heavy costs the Luftwaffe between 2 & 3 mediums (He-111, Ju-88) or around 1-1 in Condor production
The Luftwaffe would have needed at least 1,500 heavies to make any sort of credible offensive (even that force will wind up eaten up within 4 months at 10% loss per mission). That is 7,500 fewer defensive fighters challenging the 8th, assuming the Germans do not keep putting out more aircraft.
Bombing offensives require almost ungodly amount of production. The production requirements were such that the U.S. and, to a lesser extent, the UK, could build enough bombers AND fighters. As an example the Luftwaffe accepted just about as many Do-17, He-111, He-177, Ju-188 & Fw-200 airframes combined than the RAF accepted Lancasters and the U.S. produced almost 4,000 more B-24s than the Luftwaffe did Ju-88 (while also building about 12,000 B-17s, 10,000 B-25s, & 5,300 B-26).
Of course you then run into my favorite STUNNING production number, with the U.S. actually building 7,500 A-20 Havocs (I mean, the A-20? Who knew???

).
Overall, I'd say that if the Reich had decided to build a couple thousand heavies, Hap Arnold would have sent them champagne.