upsides to making a portal to heaven  
    to   build   the   factory  there   
  
                                          
 first  of  all, real estate: the  highly 
 fractalized  geometry  (not  proven  but 
 likely  to  be the case)  implies almost 
 unlimited room;  even if the portal tech 
 would  be  stolen,  chances  of  running 
 into  a  competitor  is  close  to none, 
                                          
 secondly,  the  resources:  heavens  own 
 alchemical  properties  (proof   exist!) 
 makes  most  base materials  easily  and 
 readily  available.  once  the molecular 
 movement  patterns  are mapped  out, any 
 compound  can   be   created   virtually 
 without                            cost. 
                                          
                                          
  
  downsides  to  making  a  portal to   
  heaven  to build  the factory there   
  
                                          
 current  portal  tech  takes some energy 
 to hold open,  which isn't  a problem in 
 itself. test  results however  has shown 
 that without an  active tether, heaven's 
 time flow breaks  down completely.  even 
 a  momentary fluctuation  of the  portal 
 would    render   all    remote   assets 
 practically  lost.  much  care  must  be 
 taken  to  maintain  portal   stability. 
 (one  option could  be  several portals)