There is nothing wrong with putting the bot in the rumble. As long as it has no 'hard coded' names, and it does not look like you did this, it is a completely valid concept. Beside, it effects the score not like you guessed, in fact it is quite the opposite.
Generally ram bots have a very hard time in melee match ups and your bot will have an even harder time to survive. Most bots (even the strongest) target the nearest target (especially at round start) and so it depends who is the nearest bot to you at start. This effects the score in no way so it is valid. The next round you run all the way through the field to reach your first target - let me say this, you never reach the target because you will die on your way with a very high probability. This also effects the score no more than every other bot would. And you start a new list for every battle, most bots maintain a 'danger/target' list to decide which bot might be worth to engage.
I had some test runs with my usual melee test battle files and could not see any influence at all. Maybe you can say something about your test run with Shadow, there might be something i don't see right now.
Anyway, I woud say 'bring it on' and good luck :)