This looks like its moving in the right direction but needs a bit more debugging and testing. If I try and run hammerdb from another directory, I get:
Error in startup script: couldn't read file "./HammerDB-4.8-600/hammerdb": no such file or directory
This is because it is trying to execute the absolute path rather than the relative one.
exec wish8.6 -file $0 ${1+"$@"}

So this looks like it needs the same change as the agent e.g.
exec .././bin/tclsh8.6 ${0##*/} ${1+"$@"}

However, there are other tests I did that get broken with these changes such as running the automated scripts such as:

./scripts/tcl/maria/tprocc/maria_tprocc.sh
BUILD HAMMERDB SCHEMA
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
can't read "LD_LIBRARY_PATH": no such variable
    while executing
"export LD_LIBRARY_PATH="./lib:$LD_LIBRARY_PATH""
    (file "hammerdbcli" line 6)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
RUN HAMMERDB TEST
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
can't read "LD_LIBRARY_PATH": no such variable
    while executing
"export LD_LIBRARY_PATH="./lib:$LD_LIBRARY_PATH""
    (file "hammerdbcli" line 6)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
DROP HAMMERDB SCHEMA
can't read "LD_LIBRARY_PATH": no such variable
    while executing
"export LD_LIBRARY_PATH="./lib:$LD_LIBRARY_PATH""
    (file "hammerdbcli" line 6)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
HAMMERDB RESULT
can't read "LD_LIBRARY_PATH": no such variable
    while executing
"export LD_LIBRARY_PATH="./lib:$LD_LIBRARY_PATH""
    (file "hammerdbcli" line 6)

So it needs testing with the hammerdbcli auto argument with both Tcl and Python options.
There is also an auto argument to the GUI that will load a file and run the autopilot that needs testing as well.

It needs testing from local and remote as another error I saw running locally was the following:

./hammerdb
While loading module "tkpath"...
can't find package tkpath
    while executing
"package require $m "

On Linux a quick hack showed something like this worked a bit better, however I cannot guarantee it satisifes all test conditions:

#!/bin/sh
########################################################################
# \
cd "$(dirname "$0")"
# \
export LD_LIBRARY_PATH="${0##*/}/lib:./lib:$LD_LIBRARY_PATH"
# \
export PATH="${0##*/}/bin:./bin:$PATH"
# \
exec wish8.6 -file ${0##*/} ${1+"$@"}
# \
exit
########################################################################

On Windows a basic test worked, however I have not tested all scenarios such as running the scripts from Powershell.

So if this has been thoroughly tested then the idea is good, however we need to be absolutely sure that it doesn't break some of the functionality inadvertently as this is the reason it has not been done already as changing to the home directory before running we know for certain every test is passed, so we need to have the same confidence with these changes.