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)