I managed to install the following last night on my Windows 98 OS:
Bdash
TDD
BGT
DSotSC
World Map
TDD fix 6
Ascension, your new installer worked fine every time I ran it (including on some installs I screwed up in other mods)

(with a soft drink). I checked the above installation success after Bdash,
TDD,
BGT and
TDD fix 6 were run, and I was able to start a new game at each step.
TDD could use a lesson from you, however. The install does not clean up the folders. Remember the "Invalid switch - /S" problem with 099b1/b2 and 95/98/ME?
TDD appears to have the same problem, and left me with the following extra folders:
DLGCSH
TDD-ARE
TDD-BAM
TDD-BCS
TDD-CRE
TDD-DLG
TDD-ITM
TDD-MOS
TDD-RULE
TDD-SFX
TDD-SPL
TDD-STO
TDD-TIS1
TDD-TIS2
TDD-TIS3
TDD-TIS4
TDD-WAV
I was also left with a SETUP-~3.DEBUG file, which follows:
**************************************
WeiDU v 188 Log
F:\BLACKI~1\BGT100B3\SETUP-~3.EXE
[./Chitin.key] loaded, 738659 bytes
[./Chitin.key] 274 BIFFs, 52177 resources
[dialog.tlk] loaded, 11846000 bytes
[dialog.tlk] 93082 string entries
[./Autorun.ini] loaded, 1452 bytes
[./BALDUR.INI] loaded, 3184 bytes
Possible HD/CD Path: [F:\Black Isle\BGT100b3\]
Possible HD/CD Path: [F:\Black Isle\
BG2\CD1\]
Possible HD/CD Path: [F:\Black Isle\
BG2\CD2\]
Possible HD/CD Path: [F:\Black Isle\
BG2\CD2\]
Possible HD/CD Path: [F:\Black Isle\
BG2\CD3\]
Possible HD/CD Path: [F:\Black Isle\
BG2\CD4\]
Possible HD/CD Path: [F:\Black Isle\
BG2\CD5\]
[./Keymap.ini] loaded, 5615 bytes
[./Mplaynow.ini] loaded, 230 bytes
[F:\BLACKI~1\BGT100B3\SETUP-~3.EXE] Using scripting style "
BG"
[dialog.tlk] claims to be writeable.
[dialog.tlk] claims to be a regular file.
[
WeiDU.log] parsed
[SETUP-~3.TP2] parsed
SETUP-
BGT.TP2 0 0 Installed
SETUP-
DSOTSC.TP2 0 0 Installed
SETUP-
DSOTSC.TP2 0 1 Installed
SETUP BP-
BGT WORLDMAP.TP2 0 0 Installed
SETUP BP-
BGT WORLDMAP.TP2 0 2 Installed
SETUP-
TDD-FIX1.TP2 0 0 Installed
Install Component [Game Graphical User Interface (GUI)]?
[N]o, [Q]uit or choose one:
1] "Baldur's Gate Trilogy" (Elminster wielding staff)
2] "Baldur's Gate Trilogy" (Elminster wielding sword)
3] "The Darkest Day"
Uninstalling All Other Subcomponents of [Game Graphical User Interface (GUI)]
Done Uninstalling All Other Subcomponents of [Game Graphical User Interface (GUI)]
Installing ["Baldur's Gate Trilogy" (Elminster wielding staff)]
Copying 1 file ...
[GUIlist/3/GUIOPT.chu] loaded, 10238 bytes
override/GUIOPT.chu copied to GUIlist/Backup/0/GUIOPT.chu, 10238 bytes
Copied [GUIlist/3/GUIOPT.chu] to [override/GUIOPT.chu]
[GUIlist/3/guiverb.mos] loaded, 140304 bytes
Copied [GUIlist/3/guiverb.mos] to [override/guiverb.mos]
[GUIlist/3/start.bam] loaded, 16169 bytes
Copied [GUIlist/3/start.bam] to [override/start.bam]
[GUIlist/3/START.chu] loaded, 1960 bytes
override/START.chu copied to GUIlist/Backup/0/START.chu, 1960 bytes
Copied [GUIlist/3/START.chu] to [override/START.chu]
[GUIlist/3/start.mos] loaded, 389464 bytes
Copied [GUIlist/3/start.mos] to [override/start.mos]
[GUIlist/3/start25.mos] loaded, 389464 bytes
Copied [GUIlist/3/start25.mos] to [override/start25.mos]
[GUIlist/3/startold.mos] loaded, 389464 bytes
Copied [GUIlist/3/startold.mos] to [override/startold.mos]
Already Asked About [Game Graphical User Interface (GUI)]
Skipping ["The Darkest Day"] because another subcomponent of [Game Graphical User Interface (GUI)] is already installed.
Saving This Log:
SETUP-
BGT.TP2 0 0 Installed
SETUP-
DSOTSC.TP2 0 0 Installed
SETUP-
DSOTSC.TP2 0 1 Installed
SETUP BP-
BGT WORLDMAP.TP2 0 0 Installed
SETUP BP-
BGT WORLDMAP.TP2 0 2 Installed
SETUP-
TDD-FIX1.TP2 0 0 Installed
SETUP-~3.TP2 0 0 Installed ~"Baldur's Gate Trilogy" (Elminster wielding staff)~
[SETUP-
BGT.TP2] parsed
[
BGT/Language/English/setup.tra] parsed
[
BGT/Language/English/setup.tra] has 86 translation strings
[
BGT/Language/English/dialog.tra] parsed
[
BGT/Language/English/dialog.tra] has 26 translation strings
[
BGT/Language/English/journal.tra] parsed
[
BGT/Language/English/journal.tra] has 311 translation strings
[
BGT/Language/English/scripts.tra] parsed
[
BGT/Language/English/scripts.tra] has 25 translation strings
[SETUP-
DSOTSC.TP2] parsed
[
DSotSC/Language/english/setup.tra] parsed
[
DSotSC/Language/english/setup.tra] has 667 translation strings
[
DSotSC/Language/english/setup.tra] parsed
[
DSotSC/Language/english/setup.tra] has 667 translation strings
[SETUP BP-
BGT WORLDMAP.TP2] parsed
[BP-BGT_Worldmap/language/english/setup.tra] parsed
[BP-BGT_Worldmap/language/english/setup.tra] has 82 translation strings
[BP-BGT_Worldmap/language/english/setup.tra] parsed
[BP-BGT_Worldmap/language/english/setup.tra] has 82 translation strings
[SETUP-
TDD-FIX1.TP2] parsed
[SETUP-~3.TP2] parsed
SUCCESSFULLY INSTALLED ["Baldur's Gate Trilogy" (Elminster wielding staff)]
WeiDU Timings
adding translation strings 0.000
COPY 0.000
load TLK 0.000
parsing .log files 0.000
saving files 0.000
BUT_ONLY 0.000
eval_pe 0.000
parsing .tp2 files 0.100
unmarshal KEY 0.110
parsing .tra files 0.120
unmarshal TLK 0.210
loading files 0.600
TOTAL 1.140
***********************************
This leaves me with another question. Other than for uninstall purposes, do the folders and exe/tp2 files for the mods necessary in the game directory, or can they be removed?
(I hope this isn't a duplicate post - my first try didn't seem to work...)