TYPO3 Core

The issue is present in v7 also.
Unfortunatelly It's not that easy to solve at first sight because EditDocumentController.php expects default values (overrideVals) to be global (same value for all edited records). It's not possible to pass different doctype for each new record.

The query sent by clicking on the "create new translation headers" icons passes following parameters:

route:/record/edit
edit[pages_language_overlay][5]:new
edit[pages_language_overlay][9]:new
overrideVals[pages_language_overlay][sys_language_uid]:1
columnsOnly:title,hidden,sys_language_uid
returnUrl:/typo3/index.php?M=web_info&moduleToken=0c38bb5cabfab80ba8350eff44dd8fc971276ecb&id=5&SET[depth]=1

I've compared it to the call sent when translating single page from within page module (which sets doktype correctly):

route:/record/edit
edit[pages_language_overlay][5]:new
overrideVals[pages_language_overlay][doktype]:4
overrideVals[pages_language_overlay][sys_language_uid]:1
returnUrl:/typo3/index.php?M=web_layout&moduleToken=43726e35b7b6d042911fe3704ad4117c0c2ae9a0&id=5

see additional param "overrideVals[pages_language_overlay][doktype]:4".

The problem is that the overrideVals is global for all records passed to the edit controller.

one more thing to add is that the list module (when translating tt_content) is doing it differently (calling 'localize' instead of 'new' datahandler command)

route:/record/commit
token:ad2e597af4b055d0400169b63d8ead687ed1eb8a
prErr:1
uPT:1
cmd[tt_content][11][localize]:1
redirect:/typo3/index.php?M=web_list&moduleToken=318cc442678e966034b8bf1a856e66476ac798c2&id=35&table=tt_content&imagemode=1&justLocalized=tt_content%3A11%3A1

M:web_list
moduleToken:318cc442678e966034b8bf1a856e66476ac798c2
id:35
table:tt_content
imagemode:1
justLocalized:tt_content:11:1

route:/record/edit
token:71ffe7bef130a0b40edd53facdb2f663127a5136
edit[tt_content][207]:edit
returnUrl:/typo3/index.php?M=web_list&moduleToken=318cc442678e966034b8bf1a856e66476ac798c2&id=35&table=tt_content&imagemode=1