If you apply to an airline that operates 73's with your 100hrs on type, you will have to be put through the operators conversion course anyway to learn their SOP's and then go on to do line training with that airline, therefore I cannot see how you are saving the airline any money with 100hrs on type therefore a TR only would probably be just as good. It "may" get you slightly ahead of the crowd in terms of experience but I've been at selection days with guys who have a TR and also a TR + 100 hours, just think how frustrated you'd be if you had shelled out £xxxx only to find out you maybe didn't have to do it anyway.
Another thing is the cost issue, if your going to think about getting a rating and some time on type and put yourself further into debt by borrowing more, then remember your going to need a good salary in order to pay it back, if your starting on a reduced salary until you get to 1500 hours then you do have to live etc as well.
I'm sure at this moment in time you maybe feeling annoyed that your not getting a look in with various airlines, it WILL come as long as you persist just don't think that throwing more and more money at it will get you there quicker, the airlines can be very picky with low hour guys because there is a good supply.
Its up to you, but there are NO guarantees!
Just my 2 cents.