The latest altsys has a feature helping to develop templates of D3 modules.
You may know "auto update feature" for conventional modules already.
eg) updating templates developping modules of xhnewbb and xhld0.
insert 2 lines into mainfile.php just after including "include/common.php".
$tplsadmin_autoupdate_dirnames = array( 'xhnewbb' , 'xhld0' ) ;
include XOOPS_TRUST_PATH."/libs/altsys/include/autoupdate_from_module.inc.php" ;
$tplsadmin_autoupdate_mydirnames = array( 'd3forum' , 'aaaaa' ) ;
include XOOPS_TRUST_PATH."/libs/altsys/include/autoupdate_from_d3module.inc.php" ;