ITs possible to force a device to specific power level. But remember - in noisy environment - You will also amplify the noice.
Now this needs a little explanation since it makes no sense. IMHO the noise gets amplified on supplemental Rx amplification, not on Tx, where only the S/N ratio gets boosted.
Unless you mean the spectral purity of the signal, which is something entirely different and is possible to be degraded by increased Tx power. But for devices with the proper FCC and CEPT certifications, this should not be a major issue.
Torturing CCR1009-7G-1C-1S+, RB450G, RB750GL, RB951G-2HnD, RB960PGS, RB260GSP, OmniTIK 5HnD and NetMetal 922UAGS-5HPacD + R11e-5HnD in my home network.